when i got my 69 camaro, i got it, because "a", i won it in a bet, and "b", it was a 250 6 cylinder, and it wasn't really worth restoring because of the engine size and basically a bone stock car, so i decide to tub it. that was the main goal from the beginning. so if your car is basically a standard or bone stock car, do what you want to it. if it were mine, i'd say good bye to the 307 and hello to big block, but a 350 wouldn't do to bad either. do like steve said, hold on to the parts that you remove and keep them for a rainy day. you never know, somebody might need them some day.
just have fun with it.