The big issue with the 1990 350 is going to be the computer controls. If you have money, then it is not such trouble, but if you are driving a 66 chevy that is worn out, then that means you dont have that kind of money. In my opinion, you would be much better off, and save thousands, as well as have a good running easy to fix truck if you stuck with non computer controled engines.
The 69-79 350's are CHEAP to run and fix, and you can squeeze good gas mileage out of them as well, with some informed research. The cheapness allows you to run higher grade parts for the same price as other engines. Personally, if it were me, I'd stick with the 283, rebuild it, then swap in a newer 4 speed overdrive transmission, a non electronic model, available through many sources rebuilt stronger than new. The newer trans' give you lower low gears, for more power, as well as overdrive, for better cruise and mileage. A good transmission selection, with proper diff gears, creates more power than than thousands in hop up parts. You will have a LOT more power on takeoff, as well as a longer lasting, more efficient engine. I'd rather have a 6 cylinder with a 700r4 trans than a 402 with a powerglide. As well, a 402 with a 700r4 will get better mileage than a 6 with the glide.
