Koji, Welcome to the forum. A few things to check as you go thru.
DeTomaso motors are basically Mustang motors as Doug mentioned, they were pulled from the line before getting serialized. 8MA1088 would have been built late 1968 to mid 69. I doubt it ever had a 289 only very first handful of cars may have had 289HiPo .( Check dates on glass - that will give an estimation on build date. Motor casting dates should precede this date.
Your block should not have a short VIN stamped on top rear flat area ( that was for FORD cars). The DeTomaso engine VIN is on the intake.
Castings on 302 heads are under the head when bolted down and dates are under then valve covers, so very hard for anyone to ID when all assembled. Water pump date impossible to see when on car. Block and intake casting and dates relatively easy to see. It is fantastic to have all original if not you can search for properly dated components. Assuming you have the original intake look for engine block casting date very close to that date. PM me if you need more info.