I ordered the lg4 TES headers before I swapped in the 350, and
it had the 2 1/4" y-pipe. An exhaust shop modified it, but it is
messed up and needs to be replaced. I was wondering if the
3' y-pipe and the cross over pipe for the TPI TES kit would bolt
right up to the lg4 kit headers.

 

no, the tpi pipe will not work... Been there, done that. The LG4 has the early evap crap on the exaust manifold on the pass side. The TPI TES headers have doughnut gaskets on both header to y-pipe fittings wile the LG4/L69/TBI TES headers have provisions for that valve there that rederects exaust. The tpi y-pipe will not fit.

edit: On a side note, the pipe might work, might. The valve body might fit in the same place as the doughnut gasket but i suspect that there would be alighnment problems since the casting will take up more space then the gasket they use. I suppose you could try it or give edelbrock a ring. Worse comes to worse, youll jsut have to return the y-pipe. Just make sure you dont damage or molest it in anyway in case it doesnt work out. Oh, BTW, youll be waiting at least a month or more to get the y-pipe. They're back ordered to hell...