3969854 block casting number belongs to a 402 Big Block produced between 70-72. 2 and 4 bolt had same numbers.

3975950 head casting number is for 396/427 produced between 68-70. It has 2.06/1.77 valves and closed chamber oval ports.

TBG = 1970 Truck motor, 402CI with 310HP and originally bolted up to a TH400 automatic.

Good strong motor as a base for a BB rod..

Regards,
Glenn