Hey there Dave, Couple of questions, why on earth would you want to go to 4.4 ratio? Have one in my 70 Zed and it drives me nuts, I only get to drive it on weekends so I don't know how you will go as a daily d. Great for circuit work though, brilliant at Lakeside, back in it's day. You will have a real short relationship with first, so you will want to groove your syncro's in first and second if you want real quick changes form the box. Mine ran a 13.1 @ 109mph with this diff and with 165kW @tw, should be quicker with the weight of these cars. Currently changing it to a 3.7 or 3.9 from an 83 280ZX, as these came with an R200 and CV shaft rear and disc brakes and I dont need to go on. Second Question, how do you find the cam profile in relation to boost? The 280 also has a turbo/inj 2.8 so I'm looking at transplanting that into my 240. Lightening the flywheel for a bit more fun. Was a nat asp version so if anyone can give me a hint on cr for these would be appreciated. And it certainly looks like you are having a bunch of fun. Any pics on the 510? Drew.