1hz
some folks helped me out here--a little different app---1hdt with h55 in a 40 but good p/ns etc in the links
https://forum.ih8mud.com/diesel-tec...1396-real-time-help-id-series-lc-motor-2.html
If I got it right then the 1hz came with 275 mm clutch and the 1HDT came with a 300 mm clutch
you already know the blocks are the same I assume and are just wondering on tranny matching?
To put the 1hdt into my 40 with a h55 I can use either I have been told but I need to use the 1hz fine spline input shaft in my h55 but you would already have that I assume
https://forum.ih8mud.com/diesel-tech-24-volts-systems/245813-1hz-install-into-1978-fj40.html
https://forum.ih8mud.com/40-55-series-tech/421559-r151f-1hd-t.html
" a quote here" by rick d in one of the posts
the connection to a cast iron H55 transmission is made with a HZ input (can go in any october 1985 or later H55), either the 275 HZ flywheel or better the 300mm HDT flywheel, for disks = 275 use std toyota HZ for 300mm use an Isuzu NPR clutch disk, then correct pressure plate.
this info is all from the 3 or 4 posts I did on the 1HDT swap into my 40
hoping to get you pointed the right way I have no direct experience with it yet and was just asking similar questions but with a different tranny--the h55
seems to me that since the blocks are the same you should be able to swap everything over from 1hdt to 1hz--my prob is the other gearboxes are too long for my 40 so i have to go h55 and modify the input to match the 1hz/1hdt set up
if the 1hz is saveable and you are just looking for turbo power you might want to read crushers 1hz turbo thread