Easy way to tell the difference between a 305 & 350 is the harmonic balancer,the balancer on a 305 is about 3 inches wide,350 4 bolt is like 2 inches wide,but 7 1/4 inches in height,350 2 bolt is 2 inches wide but 6 3/4 in height. 305 H.O. and 350 4 bolt have a oil pressure plug above the timing chain coming from the cam journal,a few 350 2 bolts had them but not many.