Make sure you follow each step as written in the document. Just because you already did it doesn’t mean you should skip it. Happened to me a few months ago
https://www.vortexbuicks-etc.com/no_start_tree.htm
There is some surface rust but they worked fine. I was running 27# and vacuum brakes and didn’t had any issues. Took then off because I’m relocating the hoses to the plenum
Port it to 1.15-1.20 ish. You have plenty of material to work with in there. Just try to keep it even all the way around.
you could grab abottle cap that’s slightly bigger than the current hole and mark it in the housing with a sharpie then take material using the mark as reference
Got mine from summit. Whatever material the summit brand ones are. Can’t beat it for $110 shipped. Haven’t been able to drive the car yet.
And they came with all the bushings, including #5
The converter is almost an inch taller than the flat rate box. Maybe have the shipper try to refold the bottom flaps of the box to make it fit and look flat on top
IF your post office is cool, it will fit on a large flat rate box. If they are picky then no. but for reference, a 32lbs label from UPS will do the trick