Z90- Commercial Chassis
6-368 4bbl carb (standard on commercial chassis)
A-1980 model year
195116 Chassis sequence
Is there a casting number anywhere on the block? This may help ID the engine.
368's had casting numbers of 1615255 or 1620734
There were a couple of different combinations of 368s offered:
VIN code 6 were 4bbl carbs offered on 1980 Cadillac RWD passenger cars and hearse/limos
VIN code 9 were DFI in the following manner
1980 Eldo/Seville Digital Fuel Injection (TBI) no modular displacement
1981 Eldo/Seville/RWD/ Limo DFI with modular displacement. (the hearses used carburetors (VIN 6))
1982-84 Limo used Vin 9 (DFI with modular displacement)
1982-84 Hearse used VIN 6 (4bbl carb)
1982-85 RWD sedans used the HT4100, a Diesel, or a Buick V6 until 1982.
If you have the original engine, it appears you have a 368 with a 4bbl carb, as was standard for that chassis.