Which tranny for my vx swap
 

I am placing a d15z1 in my 89 dx. I was pondering changing the dx tranny for the cx/vx that actually belongs to this engine, but they hard to come by for a decent price. I have access to a crx hf tranny, i do not know which one it is though. Would my dx tranny run the rpm's too high if I just kept it, and also, would the hf gears be a bit too long and make my pickup speed suffer greatly? While I'm asking questions, will the hf tranny fit the z1 and my hatch with my current mounts?

If you were to install the z1 trans into the 89 hatch, it does have a different front engine mount and the clutch is operated with a hydraulic system whereas your 89 civic uses a cable operated clutch. All of this can be custom made, but that is a lot more work to add to the swap.

I can't be of much help with the gearing differences since I seem to have misplaced the link I had comparing the different gearing for the different d-series trans.

Just found the gear ratio lists I had lost.

https://www.geocities.com/bing_bong916/trannyspecs1.html

Well I thought I found the one and copied the link wrong, but this should help. This was copied off of d-series.org, a very good source for reliable specs for Honda d-series trans.

Yes, the hf trans will fit your z1 with the stock trans mounts, thats what I put in my 90 hatch. Its probably your best option, cable clutch and ratios at least as tall as the original vx one. (I'm turning about 2k at 70mph) I'm very happy with mine. First gear is maybe a little taller than I would like, but the dx trans would rev too high IMO.

For simplicity's sake I would say that the dx would be fine. And if you feel your not getting the mpg's you would like you can always change it down the road.

Your swap might go smoother one step at a time.