3.1 ROM upgrade

[Oldsmobile_Mike]

I could only count 19 pins on the rom due to the lighting and angle, which makes it hard to tell what is going on. They may have stuck a sticker on a random 38 pin chip for the photograph, but it could also be that it's screwing with my eyes.

Must be a difference of your monitor.  His picture was clearly identifiable for me, on my phone and on my computer.  Either way, it's still good information.  

Edit, just re-read the question.  OP, are you saying your chip has 42 pins and your socket only has 40 pins?  IMHO I'd just buy the proper ROM from AmigaKit, they're available new for <$20 USD.

[Oldsmobile_Mike]

That's the way I installed it, with pins 1 & 42 (by the notch) hanging over the end. It's supposed to be a regular 3.1 (licensed from Cloanto). I didn't think of AmigaKit at the time!
Mike- Yes socket 40 pins- 1.3 ROM 40 pins - 3.1 ROM 42 pins

You say Cloanto.  Is it a standard 3.1 ROM or the special Cloanto "3.X" ROM?  If it's a 3.X, you may have it installed properly, but have myriad completely unrelated problems because of the changes they made in it.  

What color is your screen when you try to boot with the ROM installed?  Any clicks from the floppy drive, does the power light go bright or stay dim, stuff like that?

[Oldsmobile_Mike]

Interesting that the picture in the auction shows a standard 40-pin chip.  Of course everyone uses stock photographs not photos of the actual product, so that's not really anything to go by...  

IMHO if a seller won't respond to messages after a reasonable period of time it's some kind of scam.