GM TBI is meant to be used on stock engines. If you head over to the third gen TBI BBS, you can dig through the largest stash of TBI tuning data on the web. You can modify TBI to work on many applications, but rest assured, to get your A/F ratio correct on even a mildly modified motor you are going to have to do some PROM tuning. Bumping FP is not enough, and will lead to other problems. The larger the cam, the more problems you will run into.
Yes, there are guys here, and elsewhere, that run built motors with factory tunes, etc., but I've never seen a single one of them post a A/F curve for us to look at. Assuming that it works because it doesn't blow up is foolish. The early 454 TBI trucks ran lean from the factory, and that lead to melted pistons, etc, using the factory tune on a stock motor.
Take your chances if you want. Or do it right and don't worry about it.
Aftermarket heads are the way to go, perhaps some Vortecs if you're on a budget.