Right now you have a virtually unmolested truck. Once you commit to that swap, there is really no turning back.
The V8 will require major steering modifications. The TH400 will have you chopping holes in the floor, or changing out the steering column, and will require a different radiator. Now your truck will give you speed that the factory brakes weren't designed for.
Don't get me wrong, I like street rods. I just hate to see a stock truck get butchered, when there are so many others that have already been altered to use for street rod material.
But hey, it's your truck and your decision.

Good Luck
John