I'm aware The GMC 300 engine is a big tough engine. It is very heavy. But I believe you will be going backwards putting it in a 68 model truck.
Do you know what was originally in it. You can tell by the serial number weather it was a v-8 or 6 cyl.
I think you would be better off putting a 292 or 250 6cyl. in it. or a small block v-8. That would be almost a direct drop in
swap. Any modification needed would be readily available parts. You might even have to change the front springs to use the 300 engine
I'll agree the T-5 transmission would be a great addition for what ever engine you use. I have put in several of them. You may won't to consider
one with the .o73 o-drive ratio instead of an .086. It depends on what engine you use.
George
