412 Diff Ratios/Gearing Upgrade

[peasantslife]

Greg, yes thank you, I am aware that there are detail differences in spec's across derivatives and years within ostensibly a common case. the good news is that there appear to be just two interchangeable gear sets for 727 and 518, several valve bodies and everything else is tuneable - solenoids, clutch pac's and bands. Also there is a thriving US home rebuild/upgrade market for these things, so I'm not at all concerned for proving the concept with a less than perfect example, though I'm inclined to buy 'good working order' and then at whatever stage rebuild the trans to my own requirements. I confess I am impressed with the very soft shifting my current box delivers at part throttle, if it were'nt for the tacho and nvh one would hardly know the shift had occurred at all. I dont recall the AMV8's shifting so imperceptibly when new....And a soft shift is not ideal for overall longevity, as it puts friction materials into suspension.
As I've previously mentioned, the firm I'm in converstion with are specialist US factors, and they have already told me they supply several of the well known 'Bristol' specialists - the mentioned names probably known to us all. They also supply engines/trans/anything for the 'Yank' custom performance markets in UK and Europe so build or just supply with lashings of knowledgeable experienced advice. The bit I dont know is of anyone who has actually done the installation work at home, or who owns a car with a 518 lockup in it to comment on how it changed the characteristics which frustrate me. I think I've probably gone far enough now to put this on the back burner til ready to start. In the meantime out to the garage now to build a new axle for the Winnebago, and then take the skin off an aston...and that will be this year gone!