Complex sentence: The MICV program continued on and in 1972 a new request for proposals was issued which was won by FMC and they began construction of the XM723 prototype which was completed in 1973.
Split into simpler sentences: The MICV program continued on and, in 1972, a new request for proposals was issued. This was won by FMC, who began construction of the XM723 prototype, which was completed in 1973.