GMC 302 street engines are expensive to build,no performance parts a readily available,as compared to other engines.Realistic street hp is around 250 before you get into even more expensive modified heads etc.Racing 302's have mega power,but they have little to nothing in common with street engines.But the 302 is a fantastic piece,the best vintage engine by far,but not exactly light or compact.
Light and compact?,a supercharged 250 Chevy might be a good choice,uses readily some available small block V-8 parts,should produce 275+ HP easily without becoming too nastly for regular driving.The AMC,Mopar or Ford inlines are also will fit the description.