Small block headers: worst to best fitting. List your experience.

Worst to Best in a mid-gen A:
Cyclone/Blackjack with Alumi-kote
Went in OK (67 A-body), but trying to tighten the bolts to the head, on both sides the tubes near the collector contacted the chassis.
Returned them. Went to used 340 manifolds instead.
A couple weeks later my friend's brother is putting a non coated set into his full size Blazer. They don't fit either. But he was more determined than I was and exhanged them for another set, which did fit.
All I can say is a if header assembly jig is so bad that they won't always fit in a full size Blazer, sumptin is wrong!

TTI-Shorty (early production)
Spent a lot of time trying to get the head pipe to clear things. Too many changes needed. Sold them.

Custom
Install went great - most of the work done by the builder. It wasn't easy but it wasn't terrible. I've had to take the driver side off a couple times and its a little time consuming but not difficult.

Headers By Ed
By far the easiest install. Both sides are multi-piece with flanges. Only downside is when driving on bad streets the primarys get dented.