GTO manifolds flar away from the engine so much that the outside of the collector makes contact with the frame rails, and the dump location/angle is not good either. I have pics of this somewhere at home, and a side by side of the manifolds on my build thread.
The truck manifolds may fit and they have larger/same collector outlet sizing as the C6 manifold. I'd use them if they fit.
I'm using the TBSS manifolds, they are similar to the truck but the outlets are in a slightly different position and the collectors are smaller
'But they fit like a glove'
To me it looks like the truck manifolds have a good chance of fitting. Have you tried them?
They will have more internal volume than any other manifold, and the collector outlet is positioned and angled to the 'k member windows' on either side of the engine. Only thing is, with the granny mounts I think one side may get close to the firewall?
I understand the time/money thing. two kids at home, opened a new card to put my tune and misc expenses on then promptly used up most of my credit line on hospital bills for the infant, after that the 2 year old poisoned herself and we paid emergency hospital bills on that. hahaha sigh.
