To fit the 71-series automatic, Datsun fitted a larger tunnel to the auto 1200. You can fit this tunnel to any 1200 rather easily, and it seems to be identical to early B210 and 610 tunnels (pre-catalytic convertor). See Tunnel.

With more torque than a stock A14, it is recommended to fit a larger differential. The H150 can only handle a little more torque. It is recommended to fit an H165 for use with a 2.4 liter, or with a turbo 1.8. They cheap swap is an H190 out of a Datsun 320 pickup, it is however it little narrower than than the 1200 rear axle assembly.

would an auto trans fit the 1200 tunnel? my thought is stock for reliability and decent power with about 70% more than my A15) w/an auto will make a nice daily.

what about rear end - I assume stock 145 pumpkin wont be strong enough - will 150 from a 210 do it?

A stock KA24DE from 240SX is the way to go: 2.4 liters and 156 hp. A built KA has problems.

Another choice is the SR20DE, if you like high-revving it. They can be reliably built to 150 HP or even 175 HP.

so after a few years and a few thousand miles I'm toying with the idea of more power / bigger motor. The A15 I built is pretty decent but I feel like it needs more power.I believe Ernie thinks KA is the way to go and as he's managed to burn thru a few motors and a multiple swaps this seems like a decent way to go but am wondering about possible motors as well. Nt really interested in turbo as seems like it always eats tons of space in a 1200 engine bay, would also possibly entertain an automatic vs. a stick if enough power can be had out of a mildly built KA or some such.

A manual trans swap would probably be easier as its already a stick, pedals, etc...
What did KA's come in that were rear wheel drive - frontiers, Exterra's, 240's ??

Just at the thinking stage now and it may never get beyond that but I am tempted so any thoughts are appreciated!
E