I have been really thinking about 915 box, most questions are now covered. Only problem with T1 box, even with latemodel built "zigzag" case transaxle might not be strong enough to some applications.
Even i know that these latemodel transaxles have handled 450hp honda turboengine for a while with street tires without visible or hearable damage.
Maybe if i would build smaller than 2500cc/240hv/250nm engine, then i would perhaps chosen T1 transaxle. Probably the quaife and weddle gears can handle easily more than that, only R&P weakness gets me thinking. Sure the good billet cover and weddle R&P would be big step.
It just that 915 has a lot bigger gears and ring + pinion. Early mag cased also has wey good ratios for bic cc beetle.
I first thought that i could do with 4-speed, but close ratio 5-speed sounds even better - better acceleration
Here is this current built transaxle what i am selling:
http://cal-look.no/lounge/index.php/topic,16196.0.html