Slant 6 power issues

If a slant six won't run at TDC, then something is wrong. You probably aren't really at TDC when you think you are. Find the actual TDC instead of just lining up the harmonic balancer and you'll probably find out that you're off by quite a bit.
I know what TDC is. Intake and exhaust are were both closed on cyl 1 when I put the distributor in. It tried to idle for a few seconds and died. I advanced it literally as little as it pull let me. And now it is where it is. It runs. It idles and revs fine in Park but in gear it’s just, meh. It runs fine, but it just feels gutless. It may also be worth noting that it seems to do better in reverse than in drive