Slant header ID?

Just like you,, I had troubles fitting headers.. The difference being that mine are in a Valiant,, not a truck. As a solution, I ended up modifying my Clifford headers to make things work out better on my six. I found some ancient Edelbrock headers from a Chebbie that had ball flanges and welded them on after cutting the 3 bolt flanges off(always leaked and drove me nuts). This was my third set of headers on my car..... The first headers hung too low and dragged on speed bumps, frustrating(and the K Frame had to be notched)... The second set was ugly because I had to use scrap pieces from an exhaust shop to build them(I couldn't afford to buy tube back then). Then the third set, and still running them today, I have ran for 22 years now, no leaks..... If anyone wants to see a picture, I can go out and take one.

I hope your shorties work well, that is what I used and cut the collectors off of. I ended up putting a heat shield around my starter to help shield it from heat. It came off of a Dodge Diplomat.