It is a Macgregor/Venture 21. The foredeck hatch was an option back then, as was the kick-up rudder; it appears you got the "stripped down" model. The spreaders are not missing. I think the early models had a simple tripod rig without spreaders. It is a simple boat but VERY fast.
My first "cruising" boat (meaning it had a couple of berths and room for a porta-potti) was a Venture 21. We had it for two years back in the 70s and then moved up to a huge (to us) Venture 23 which we still have.