Engine stalls in gear

what is the stall speed of your converter? Also do you have a big cam? I am assuming it shifts kinda hard into reverse?? or in drive for that matter.

I have had this problem a couple times. The more I increased the idle speed the worse it got. Sounds like your stall speed for your converter is too low. Once you shift into gear you rpms drop, vacuum drops and you stall. I drove like that for a whole summer.....two footed. Turn the idle down a bit and see if you can shift into gear then without stalling. If you can I would say it is converter. I went to a 3000 stall in my coronet and a 3000 in my scamp and the problem was fixed after carb adjustments.

It also doesn't hurt to check the other suggestions as well. Timing especially. Good luck.