s13 gearbox internals??

[30psi]

Unfortunately it does seem the S12 gearboxes are a bit of a weak link, with about the same strength as the S13 ones.

I've look at bellhousing swaps before.

I haven't looked at the comparison behind the mk1 and mk2 bellhousing bolt patterns. But I'm assuming they're different. I am also assuming though that the mk2 shares the same bolt pattern as the s13 box

Get an S14 box. Get a wrecked S12 mk2 box (i have one)

Removed the bell housings off each, and bolt the S12 bell housing to the S14 box.

Then see where you stand with the props. You might find a mix of mk1 and mk2 props might give the required length.