that's cool my first Datsun was a orange 77 short bed with a l20b and a 5-spd transmission. my second was a 78 Datsun 620 extended cab. it has 15 wheels and tires vs the 14 inch on the 77. it had better gearing I think the 78 probably had like 3. something gears while the 77 had like 4.30 gears or something really low gearing??? my 93 Toyota had 3:58:1 gearing. my next truck a 99-2004 Toyota Tacoma 2wd will have 3:42:1 gearing. i'm going to run 18's on the factory gearing. I will have it built to auto cross and probably be turbo'd too!!! you should auto cross your 620!! I bet it would do real well too!!!