Cannot find casting number BB RH exhaust

Hi,

I scored these mani's at the local pull-it yard the other day off a 75 CBody (Newport) w/400ci. The numbers are;

3830800 - Left
3830620 - Right

I have sound some infor on the left mani confirming it is for 75 but the right I cannot find any info at all. It almost like it never existed! lol

I was just trying to confirm if these were a matching set as the heads that were on this 400ci engine were mismatched. Matching or not it was still a score at $15 bucks each.

I'ts just weird that I find absolutely nothing on 3830620 Has anyone come across this casting before?

Secondary question... Has anyone attempted to use 3830800 on a BB in an Abody?