If you don't have a lot of money and you have a good running slant, I say stick with the slant.
I can guarantee you will run into problem after problem trying to put a v8 in it. Unless you know someone whos good with mopars or have a ton of spare parts laying around, you'll get nickel and dimed to death to the point where you'll regret you even started. And nickel and dimed means $20 and $100'ed to death these days.
You're going to have to trust that the v8 is in good working order. Same goes with the transmission. You may put it in and realize it needs a water pump. Then it wont start and needs a tune up and a carb rebuild. Then you realize compression is low and the tranny slips. Now theres a vacuum or exhaust leak. You just never know what you're getting when you try and build a car on the cheap. You can either get lucky or you can run into so many problems that you could have spent the same on a good tranny and rebuilt engine and been in the same place.
If you're young and don't have a ton of money but still have a good running slant, my suggestion is to do like I did and super six it and go with a new exhaust. Later on when you start making good money, you can start playing with the v8's. My slant is perky but it will not win many races with any kind of car. It's a lot faster than every other slant i've driven but it doesn't accelerate like a v8 in any which way.
Just decide what you want. A car that runs consistantly with a little pep to it for a few more hundred.
Or a car that will go faster but you'll have no idea how much money it'll be in the end because what you don't know what kinds of problems it'll have and you don't know how long it'll take to get on the road. Either way you don't want to do the first choice and then decide you want a v8. So make a decision and stick to it without turning back.
