I'm currently swapping my '73 240z L24 for a 280z L28 N42 and putting in a new 5-speed tranny. I've been getting great help from you guys and I have another question. Is there any advantage over a 280z 5-speed and a 280zx non-turbo 5-speed Tranny? And if I go with a 280zx tranny, I should get the R200 differential? I don't know much about cars but from what I've read is it has something to do with the gear ratios? Also, I live in Valencia, CA. about 30 miles north of L.A.---do any of you know of any good Z shops and also where I can find parts? Any help would be greatly appreciated.

With the stock rear end, the Z 5 spd should have closer gear ratios. The ZX has a taller 5th so would be better with a lower geared rear end.

I am planning on putting on a R200 diff in the rear anyway so would a 280zx tranny be better than a 280z?

A 280Z trans and a 280ZX (77-79) are the same trans. The 1980 and up trans has a higher first, second and fifth gear ratio with the 81-83 having a slightly higher fifth gear.