How much did you take off the heads? Did you use a pushrod checker to check what length you need? Too long , wrong angle, Nosiey? Just a thought? Man I have been there chasing Gremlins!!! Taking the performance out of the is not the awsner. It has to be timming related. Take the plugs out. take the valve covers off. Turn the engine over by hand untill you get to top dead center. It will push air out the number one plug. Both the rockers on number one will be loose. Number 6 they should have tension on them. if Number one has tension . you are on Number 6. Rotate 180 degrees. Balanance should be on zero. Rotate it to 20 degrees before. Check where distubter is pointing. Line it to # 1. put evrything back together and crank it. Timming should be set. Thats how I do it. and It should crank and run. You might have to play withthe timming,But it should be close. I like to set the valves on cynder at a time. Just how you got # 1 up turn the engine by hand, keep the plugs out . When the exhaust valve stats to open. Set the intake, Back it off till loose , the tighten till you feel Zero play the turn it a half a turn. Exhaust valve, Rotate the engine untill the intake valve stats to close. Then set the exhaust the same way. I know its time consuming, But it will be right. I only run soild cams so it set the lash like this. An Old timer showed me this way and its the only way I do it. I works evrytime. Check the push rods and Balancer first, You'll get it. Don't go back stock!! It sucks!! If you are worried about compression try a thick headgasket first, I would. As long as you are under 10-10.5:1 you should be ok. Especally if you have alumnium Heads. Just a thought. Good luck!!