I second Frankenstang65 opinion. You can get the 4 Barrel Windsor ('69 351-4bbl) or the Cleveland ('70+). I guess it comes down which ever one you can find but I have the Windsor and I notice more parts for the Cleveland but you can still find more then plenty parts for the Windsor. If your looking for engine stats and such check out
www.fomoco.com site and it will give you alot of information about different engines during the years such as hp, torque, weight, compression and such.
Hope this helped with your choice.