A very nice amp BTW. Gives that boost you need without a lot of dollars. I do not want to add to your bank account disappearing, but the next need is a dummy load that can handle legal limit. That way if you ever want to go "all the way", the dummy load will always be there.
The tuner should be replaced with one that can deal with the new amp. A 300watt tuner can flash over even if you are only close to its ratings if there is the slightest of SWR. Certain bands reacting with your antenna system and tuner can cause flash over and damage.
Some tuners include a dummy load.
Tuning of a linear amplifier must first be done at its full rated power... This model amplifier does not
have an ALC. This is an adjustment that will throttle back your transceiver to regulate how much RF the amplifer will output to the tuner/antenna.
So, you will have to adjust the ALC in your FT950 to limit the the output of the transceiver so you do not go above 300 watts. It's getting complicated here. I would suggest getting the dummy and tuner that is rated for the amplifier or legal limit rating, then you will not have to go through all of the chatter I typed about ALC's
I also see that this amp uses 4 (old days of TV) TV sweep tubes. So tuning it properly is important.
Here is a source for the manual, if you do not have it.http://bama.edebris.com/manuals/dentron/gla1000b/
There doesn't seem to be any links to free downloads.
From what I am reading from googling Dentron 1000B which is a GLA 1000B, that tuning is a little hard to understand and it must be done quickly!!!
And PLEASE use a dummy load
PLEASE........to keep interference to others using the Ham bands to a minimum.