that engine number appears to be correct for the van...qt prefix being for 308...numbers seem right for the year but if you want to know 100 per cent check the date code on the block which should be e or f 6...generally motor date is a couple of months before build date..

date code is above the timing cover below the inlet manifold staring down at the motor on the block..its cast in and if the motor is dirty is hard to see....it will be in the form of..lets say as an example only ...21E6...which would be 21st day of may 1976 ...if you can find the casting post it up here and someone will decipher it for you..