1977 c10 exhaust collar issue

[kljfamily]

1977 c10 chevy 250 i6 3 on tree single barrel exhaust manifold

I've been trying to purchase a collar/flange to hook up my exhaust to the stock manifold on a 77 250 i6. Looking online it gives me the Walker 31883 Exhaust Flange.

When it came in, it was the right 3 hole design but the holes are too far apart and do not fit the bolts on the exhaust manifold. I returned it to Oriley's assuming it was mis-picked as the box was beat up and then ordered it again from amazon making sure I had all my parameters right on year and engine size but again it was not the right fit.

Can anyone point me in the right direction.

All stock no mods stock engine and exhaust and I do not have the original part.

thanks