Decoding Engine and transmission numbers 1970 Dart Swinger 340 4 speed

block was cast Jan. 6, 1970. 2780930=casting number for all 340 blocks. R321171=last 7 of vin, R= engine assembled in Windsor Ontario. 2B=1972 assembled in Hamtramck, MI. 2881489=tapered pinion, 1.875" rear diameter and 1.375" front diameter-I do not think they came in a 1970 a body