A quick google suggests BW65 has a 1:1 top gear in common with the original 406 gearbox but the latter had a Laycock overdrive. It looks as though the LT77 has a .75 or .8:1 ratio in 5th so should be similar to the original setup with overdrive giving 2250 to 2400RPM for 50MPH from your figures.
It's a lot easier to change the diff ratio - if you can find the gears - than it is to convert transmissions so if you are happy with an automatic I would see what axle ratio options are available.
|