Hi, ive got a 79' datsun 620 4 speed. id love to put in a 5 speed with some very tall gears. what are my options? 300ZX, 200SX trannies? im just looking to get the best gas mileage i can right now. I have no idea, please help! Thanks!

A 200sx tranny bell housing should bolt up providing it's not a newer v6 or the clutch flywheel combo is not to different. I have run into into this once or twice doing a tranny swap on 620 and 720 trucks. I am not real sure what the deal was I think one of them had a flywheel that had a recessed clutch face where the clutch sat into the flywheel about a 1/2" . Sorry about the vague answers, it's been 20 years since I fooled around with this. I had a 79 620 and played around with the jets till I got a good 30 to 35 mpg running 5:13 gears out of a 67 520. It was a little screwy to drive in town but I mostly drove it on the interstate, 52,000 a year.

thanks for the reply! with your 79 620 which 5 speed did you have in it?

I used a tranny out of a 80 200sx for a while. ( I think it was an 80) It had the reverse on the wrong side. also you need to make sure the trans is the right length.They make a short tail and a long tail trans. Oh, I wound up putting the 4spd back in and let the motor scream on the interstate untill I wrecked it at about 300,000mi. I didn't run the 5spd long. Somebody with cash wanted it worse than me.