Bad Block? What's wrong?

[USMC302]

Ok here's the deal, On the 88GT, white smoke was pouring out, bad head gasket right or cracked heads apparently. Ran the test for the head gaskets and liquid barely changed color. So what the hell, we went ahead and bought new Stock heads, with new springs, valves, and everything. Got new head gaskets and went ahead and got all new piston rings as well. Got it all changed over and now engine barely wants to run, acts like it is off balance real bad with violent shaking at all rpm's, runs loud and seems to have no power, it didn't even make it down the road, it doesn't want to hold an idle either, timing is factory 10. We changed one piston at a time so order was preserved, went exactly by the torque specs, all new gaskets, oil, and all. What is wrong? Any suggestions at all? Could it be the block? I am going to run a compression test this weekend.