Thanks for the help guys.

ive got a set of each now, cant choose to eiter use flat topps or round tops.
the flat tops were off an a14 but tuned for an l20 while the round tops were off a l16 datsun sss.
So the round tops are better, but if the flattop anit pollution gear is blocked off, wont it be similar?

1.75 in sounds right
dual carb

early 240Z came with ROUND TOP Hitachi SU
260Z came with FLAT TOP Hitachi SU

The earlier (70-73) were not encumbered so much with pollution stuff and are easier to work on and provide better power. Once you get to '74( the 260Z carbs) look out. Some people have had success with them but the earlier ones are better.

Once they're tuned right you're gonna have a lot of fun!

I was told by someone on here (can't remember who) that the 1.75" SU came on the 240/260 Z. Does anyone know if they were all the same on the 240/260 Zs? I am buying one from someone, but he is not sure what size it is or anything, but it definately came off of an early Z. I am planning on getting one for my draw through set up. Thanks.