sbc casting 3970010
There is three engines with the suffix code TBM. TBM - 1970, 307, Conv, Van, C10, 1500 TBM - 1979, 350, Conv, Van, C-20, 3500, Phoenix TBM - 1982, 305, Conv, Van, C-10, 2500 To find out which engine it is you need the block casting date. The small block casting date is located on driver side rear of block on flange forward of bellhousing. Casting Date Example: E038 - (E = Month, 03 = Day, 8 = Last digit of model year (1978)). The letters A-L stand for months Jan - Dec.