so I finally got my 355 dropped into my 86 irocz and am now finidng out what a bitch the exhaust is going to be, I purchased some full length hedman hedders that said they were for 3rd gens but they don't fit and I can't return them because I used them on the test stand to fire my motor, I've tried the center dump corvette ram horn manifolds and shorty center dump headers that hug the block and neither of them fit, so where I'm at now is: I can get a hold of some z28 manifolds for free or I can put down another $150 for some shorty headers, which would be the better thing to do ?
it's a pretty hot little 355, 510/510 lift 244/244 at 050 cam, 10.5-1 pistons, bowl blended vortec heads, rpm air gap intake manifold and a 750 double pumper, probably around the 400-420hp range, I would love headers but will the shortys for the 3rd gen fit for sure, and will they be leaps and bounds better than the z28 manifolds ?

If they were made for your application then you mean they wont drop in? My headmans went in from the bottom.

no they dropped in, but the passenger side wouldn't bolt up tight because the tubes were hitting the frame and motor mount

Yea, i had that problem, i just "adjusted" where necessary with a hemmer. They work fine now.

Don't use the manifolds, they will restrict the flow and power (especially considering you are over 400hp). Try the hammer first, if that does not work move on to another set of headers.

400-420 on 750 double pumpers? thats being pretty modest. i'd say near 475 is more realistic.

When I had heddman's I had to do some clearancing myself even though I bought brand new motor mounts....So, like already stated use a BMFH!!

Go with the headers. Use the hammer, get er in there. Its a BIG difference.

You can always recover your cost by selling those huggers you bought, everyone is always looking for headers.

I have a 1992 z28 and I have hooker super competition headers on it. They are shaped really funny but they fit. And mine went in from the bottom too. The only problem I was having with mine was it kept burning up plug wires which small block chevy's with headers are notorious for doing. I went to a speed shop here in town and ordered some header plugs which are just a really short spark plug and it pulls the boots back from the headers. They were about $30 for 8 but that fixed the problem.

What plugs were you running? I run super comps and I run standard length plugs with out issue? Just curious...

you know i dont really remember that was so long ago. but i dont know what the deal was but my headers loved to eat the wires on plugs 4 and 6 constantly. it might also had to do with me running cheaper wires or something I have no idea. Im running taylor wires now and the header plugs so I should be good.