Hot Rods Small block vin ID

I need some help on finding out what this 350 might of came out of?
The casting number 3970014
the two serial numbers are 104290CMJ and 15R493600
Any help would be appreciated. Thanks John

 

350-70-76 2or4

 

• 3970014 1970 -76 350ci 200-300hp 2 or 4 bolt
• 104290CMJ 104290 - ???, eg V0101CLJ - (V = Plant, 01 = Month, 01 = Day, CLJ = Engine Suffix Code) Could this be I0429CMJ? Wentzille MO, April 29. CMJ is 1974 police car with T400 and 4bl carb or 1980 305ci Camaro
• 15R493600 1 - Chevrolet, 5 - YOM (1975), R - Arlington TX, 493600 - sequential number (Partial VIN)

 

1975 full size car 2 bolt main 2bbl 350, is my wild guess. (CMJ shows up as a 1975 160 hp 350 in a Chevrolet car)