I'm writing this to share some good results I've had in my most recent VHF mobile rig installation in a 2005 Ford F-150. I can't take credit for all of the tactics here, but I think it may be useful to folks to see a summary of what worked to avoid some common challenges. (If there is a way to post pictures here, I'll do it -- but don't see that as an option.) After probably a dozen installs in personal vehicles over 33 years -- this one has worked out the best.
Power: Using 10 gauge stranded red/black wire (I think mine was from DX Engineering, but many sources carry this), 12v power is connected directly to the battery using appropriately sized ring terminals that are crimped onto the wire and then attached to the existing clamp hardware on the battery. Take some time to think about the gauge of wire you use here depending on the current requirements of your radio. (This install is for a 75W VHF rig.) After years of soldering (its "better" right?), I went to the crimp method on these connections, along with a generous coating of dielectric / silicone grease in the terminal itself. Why? Even the aerospace industry requires crimping over soldering for power connections like this as they tend to be more reliable in a high vibration environment -- soldered connections are inherently brittle. Get yourself a good quality crimper and learn how to use it -- I'm pleasantly surprised at the results here. The power cable is routed in the most direct path down and out of the engine compartment, underneath the vehicle to a spot just underneath the passenger side door trim plate. After prying off the trim plate, I drilled an appropriate sized hole through the sheet metal, installed a rubber grommet in the new hole, and then routed the cable into the passenger compartment; RTV silicone sealant was used liberally to seal the hole where the cable passes. For places where the cable is exposed to the elements, split plastic 1/2" automotive "conduit" covers the power cable -- and all is tied in place with zip ties at convenient spots. Once the cable was routed to where my radio was going to live, powerpole connectors were installed (crimped) as I've standardized on them for all my radios.
Antenna Mount: Through the decades, I've tried many types of mount methods for VHF and UHF antennas, and by far the best results and cleanest looking installations have been with a through the roof, time-tested NMO mount. Up high, in the clear, with a decent ground plane yields consistently good performance with the lowest receive noise. (Despite the initial fear of drilling a hole in the roof -- never has this negatively impacted the resale value of my car/truck, nor have I ever had a single drop of water leak inside.) This time I used a Maxrad NMO mount requiring a 3/4" hole, and topped it off with a Larsen 5/8 wave 2m antenna. The hole was drilled on the center roof line near the rear of the roof (I look at "dead center" as the preferred location, but a truss was in that spot) and the cable was routed under the headliner, down the pillar, and over to where the radio was to be mounted. Once in place, the cable was trimmed of excess and a PL-259 was installed. Incidentally, if you are hesitant to do this piece yourself -- you may try a local commercial two-way radio dealer who installs these mounts all the time in emergency vehicles; I've found their fees to be reasonable.
Radio Mount: So it used to be that vehicles had plenty of under-dash room to mount the supplied bracket -- but, not so much anymore! We all have to be a little creative now to pull this off. For the F-150 with my particular cab configuration, the most open spot is right on top of the transmission hump. After looking at about a dozen brackets that could be used, I settled on one made by Panavise (their Model: 951-06 Universal Radio Mount), as their stuff tends to be of good quality and the adjustments available on this mount are substantial enough to accommodate a variety of radio configurations and positions. Looking under the vehicle, there is substantial clearance between the floorboard and any delicate components (definitely check before you drill!). The first challenge, ironically, was to get through the carpet -- which is a good 1/2" thick -- and down to the metal. Avoid drilling directly through the carpet -- as the bit will likely "grab" the carpet threads and bunch up the material; instead, take a large nail, hold it in vice-grips, and heat it up red hot with a torch -- and then push the nail through the carpet where you want the screws to go -- works like a charm. As for screws, I've had super success with using #10 or #12 "self drilling" stainless steel screws and a drill-driver or impact driver, after "denting" the metal with a punch a little bit so the screw won't skate around when getting started. In this case, 1" screws were used -- just make sure they are not too long for your vehicle to avoid hitting something down under. If you can get under the vehicle to apply RTV where the screws exit, its probably a good idea to do that.
After plugging everything in and mounting the radio to the new pillar mount -- I'm good to go. The result is a very clean, solid performing installation that should be trouble free for many years. TX/RX performance over the past month has exceeded my expectations. I'll definitely use this approach again in my future vehicles....