My advice is, if you are going to V8 the car in the future at any point, leave the slant alone. You will have to spend twice the money on it than a V8.
This is very true. Are you dead set on having a v8 though. Hot slants are rare and to me that makes them cool. I went down the same path as you and had a v8 in the car by the time I was 18. There are days now though that I miss the slant and the mentality I had with it. My friends and I would take the car anywhere without even thinking. Now that I am older and my car is less practicle it just doesn't happen.
DONT BE IN A HURRY TO GO FAST. Enjoy your time with the slant!