I can clarify, since I own a 240 with a Modded SR20DET layin down almost 400 horses.
The "SR20DET" came in the 1991-2002 180sx/Silvia in Japan (200sx in Australia) The "redtop" was made from 91-94 and put out 205hp with a Non BB T25 Turbo. The S13 Blacktop was in the 95-98 models and had 213hp, exact same as the Redtop, but a different color valve cover, and a slightly wilder cam set. The S14 blacktop was in the 95-98 240sx S14 and put out 250hp with a T28BB turbo, but it had Nissans HATED VTC (valve timing control, similar to toyota's VVTL-I (Not like VTEC though in Hondas). The VTC was very problematic.
All of the above came with a 5 speed man, or 4 speed auto tranny.
The S15 Silvia (only) blacktop also had 250hp, and a T28BB turbo, but it had a VERY, I mean VERY weak 6 speed tranny, which should be avoided at all costs.
Those are all RWd.....
Now, the FWD/AWD SR20DET only came as a "redtop" and ONLY put out 205hp. They were in the Pulsar GTI-R/Sunny/Bluebird if I recall correctly. Top mount intercooler, and so on, only about $1900 for a front clip.
I paid $2300 for my SR20DET Redtop front clip. (RWD). It came out of a 1993 180sx with 22k KM (not miles) on it. I have since put about $20k into my car, and the "next step" is about $10k more, so I'm done modding. My best time is
[email protected], car weighs 2270lbs (mostly stripped, and without me in it), and it dyno's at 371RWHP and 357 ftlb Tq at 4700rpm
Will a FWD/AWD Sr20DET fit into your mazda? no. Importtuner tried to put one in a Civic, but I don't think the ever finished it.
It you have the cash, then go for it, otherwise, thanks for playing.
EDIT>> Also the RWD SR20DET rods are a LOT beefier than any rods I've ever seen.

The FWD one's a smaller, and a common upgrade on the FWD's is to use the 180sx SR20DET pistons, turbos, and so on out of them...
As an additional note.... SR20DET parts are HARD to find. Many parts are interchangeable with the Z32 300zx, G20, NX2000, and 91+ 240sx KA24DE, but I'll ask you this, try to find an alternator for a SR20DET RWD. You won't find one. I had to have my buddy pull one out of a junkyard in Japan (he lives over there in ***uoka, Japan). Try to find the parts for a timing chain service. Sure, you can find the chain, but can you find the guides, tensioner, and so on? Nope. Japan only. If you don't know they right people, you can't get the parts.
