Going to bring this post back up.
I'm glad you did. Now that I read through it again, I think I added some confusing info earlier.
So if I read this correct, the part number listed in the book is different from the number stamped on the part.
Yes. Some listings say "stamped on part", but the number is actually cast into the part, so for manifolds it's typically called the "casting number".
I think that info was confusing. Marin County had a 440HP cop motor, but it didn't have HP manifolds (per the parts catalog), as it had N95 california emissions. Above, I listed the casting numbers for Marin County's manifolds, not for the HP manifolds listed in the parts catalog.
Let's work through Marin County first, since we believe its manifolds were original.
1974, w/o H/Perf, w/Calif.Emission Pkg
Right: 3751794
Left: 3837620
from parts catalog, pic here:
bluesmobiles.proboards.com/post/7122From reading the casting numbers from my maniolds (pic earlier in thread) these part numbers match to
Right: 3751794, casting: 3751724
Left: 3837620, casting: 3751071
The first post also references this casting number page:
www.mopar1.us/exhaustmanifolds.htmlwith this info on 1974
3751794 RH 1974 C 440 LP/N95
3751795 3769207 RH 1974 BC 400 HP
3769406 RH 1974 B 318. RM
3837601 LH 1974 C 400-2 LP
3837620 LH 1974 C 440 LP/N95
3837621 LH 1974 C 440 HP
The california emissions pkg was "N95" on the VIN tag, so that's these guys:
3751794 RH 1974 C 440 LP/N95
3837620 LH 1974 C 440 LP/N95
So everything matches. The casting number entry (2nd column) is empty for those rows. They could update their chart with the info from Marin County.
Marin County didn't have HP manifolds (because it had the CA emissions). The HP manifolds were:
1974, w/H/Perf
440 right: 3751795 (w/o CA emissions)
440 left: 3837621 (w/o CA emissions)
(from parts catalog).
So back to this 1974 table:
3751794 RH 1974 C 440 LP/N95
3751795 3769207 RH 1974 BC 400 HP
3769406 RH 1974 B 318. RM
3837601 LH 1974 C 400-2 LP
3837620 LH 1974 C 440 LP/N95
3837621 LH 1974 C 440 HP
Narrowing down to the part numbers:
3751795 3769207 RH 1974 BC 400 HP
3837621 LH 1974 C 440 HP
It seems there's a problem with the table. The table lists 3951795 for the 400 motor, but it's really for the 440 motor (according to the parts catalog).
At least it gives us the casting number for the Right manifold:
3751795 3769207 RH 1974 BC 400 HP
For RH, searching for 3751795 (part number) or 3769207 (casting number), I don't see much on the web.
For LH, searching for 3837621 (part number) [unknown casting number], I see this
3837621
listed here:
www.arizonaparts.com/database/partlist.txt2951860 L EXHAUST MANIFOLD U3744821,3837621 /400,440 1971-74 P,D,C,Y 1 RBY $125.00
Maybe the casting number is 2951860?