haha L series an easy fit....yeah thats a good one

they look like a really nice fit once they are in but trust me, a CA is so much easier to fit in than an L series. especially an L20b

any manual nissan box that fits a CA can also fit an L series. nissan didnt really change the gearbox design a whole heap so bellhousings are interchangable between them with very little modification

if you want to do it properly. find a D21 navara 5 speed. they are a 71C like an S13 gearbox. so just as strong as the standard silvia and R32 and 300zx and so on gearbox, but they are the shortest of those boxes. dont know the exact length but not a whole heap longer than an R30 box

any 71 series box will be a tight fit in a standard manual tunnel, so pretty much any box that came on anything from an L series through to an RB, they are all the same design of box

ive run larger tunnels in both my 1200s and both had plenty of room for the standard heater box to fit. pretty sure the maddat one is just a crap shape. in my wagon with the CA and an RB30 box there is heaps of room around the top of the box and the heater also has plenty of room

so i'd go for the newest 71 series box you can find regardless of whether its a CA or an L series, or a SR RB VG Z.
there are 3 different lengths that i know of in the 71C
D21 navara being the shortest
R31 skyline, R32 skyline and VL commodore in the middle
and Silvias, R31 pintaras being the longest
dont know where the z31 300zx and non turbo z32 would be

get one of them and you can get a bellhousing to fit pretty much any of the bigger engines nissan made from the 70s through to the early 90s