if you have the mid size output shaft the 700 is the same length the mount is 2 inches back from the 350 the 700 is so close to the 350 that a genie or lokar shifter from a 350 can be use with a little bending. If your using a column shifter the manual shaft is in the same spot the cooling lines line up . As far as pan size easyest way to see how it will fit get a 700 pan line it up with the front of the 350 pan or just use apan gasket. I have had customers do this it makes it quite obvious if the will be a problem .700s have a 3.07 first gear 350s have a 2.48 first gear you will get a much better lauch your1st gear ratio at the rear is7.44 it you just add a700 it will be 921 or the equivalat off3.71 I rub a 36 pickup with corvette 307 rear with 700 cruises at 100 mph