the Tremec is cheper and shifter can go on the box in a ton if different locations.
looking at prices a older t5 new $1300 75lbs-83lbs
the new cobra R TKO new $1800 100lbs
the 6 speed T-56 440 ft-lbs torque new $2200 115-130lbs
IMHO I would think it would only be worth it if you can get a 6 Speed. but with the stuff in CAD you will know what options there is.
it would also be good to get the weight of each too. including the spider box.
Hmmmm.... Have my mixed feelings on this whole concept, have both "purist" and "redesigner" feelings. I will say, having started Alfa's years ago on a recently overhauled 69 Berlina... that a fresh and right Alfa box was a joy to drive with.
Sounds like some serious weight gain with those boxes......
I'm raking my memory about 4-5yrs back when I rebuilt the engine on our current car. (77 Spider) I'm pretty sure the Alfa tranny weighed about 65lbs w/o oil, according to an old bathroom scale. Uh, that was before I got it reading funny trying to weigh the engine/trans together, (>300lbs) so it should be an accurate number.
I spoke to a builder at a vintage race who had installed a T-5 in a racing GTV. The shift lever was in the original position, it used the original bell housing, and original throw out bearing assembly and NO GUIBO. If you wanted to make a non-orginal tranmission swap, this sounds like the one to use.