/6 to V8 questions

The car looks to be in great condition including the /6 in it already.
You can do some fairy inexpensive mods to the engine to make it perform a lot better.
If you must go the V8 route, i would get a donor car and take what you need off of it and rebuild the front suspension etc.
Do you have bbp disc brakes on it now?
If the front and rear are bbp, you are lucky and could get away with just changing the k member to a spool mount V8 one, or get the shumacker conversion mounts.
You would need a small block 904 and the rear end would be good enough for now if you put a mild 318 in it. You also need to upgrade the radiator and torsion bars and hopefully install a front sway bar on it to do it right.
If you decide to do lots of burn outs and want a lot more power, a lot of work to change everything over like the rear diff, torsion bars, etc. would be in the cards.
What amount of power do you need?
You would probably have a hard time selling your /6 and parts you replace for very much money, even if it's in good shape.
So, my suggestion really is to buy a complete parts car and rebuild all of the parts and switch your car over, modify your existing engine, or maybe buy a car that this is already done to and sell yours as is.
Don't buy a piece here and a piece there, it will cost a lot more in the long run.
I hope this helps.