may have a rare motor

[BennyMigs]

Hello all,

I’m trying to sort out an engine that I believe may be COPO or Baldwin-Motion related. Some numbers line up, but others don’t, and I’d appreciate the community’s input.

Car VIN: 136379G339916 (1969 Chevelle Malibu V8, Framingham, MA)
Block: 3963512 (cast March 1969)
Pad Stamp: T0325JD (Tonawanda, March 25, 1969 → decodes as L78 396/375hp, 4-spd)
Heads: 3919840, date A38 (Jan 3, 1968)
Partial VIN: Present on block, faint but matches car VIN
Owner History: Motor sat in a basement for ~20 years. Previous owner claimed it was a 396, but machine shop told him it was a 427. I bought it ~25 years ago and ran it in a ’71 Chevelle.

Specs (as given to me):

425 hp before rebuild

11:1 compression, TRW pistons

Forged steel rods, 4-bolt main

Square-port “840” heads

Questions/Confusion:

Block suffix “JD” = 396/375hp, but casting is 512 (could be 396/427/454).

Heads are correct HP 427 pieces, but dated a year earlier than block.

VIN shows Framingham assembly, while COPO Chevelles are often Baltimore/Kansas City.

Car is based out of Long Island, ~30 minutes from Baldwin Chevrolet.

What I’d like to know:

Is it possible this is a COPO 427 block restamped as a 396 L78?

Could Baldwin-Motion have built it (without paperwork)?

What else should I check (casting, etc.) to confirm?

Any insights, corrections, or leads on documentation would be greatly appreciated.

Thanks,
Benny