As far as trans fasteners and such, I have been running for some time now aluminum trans pan bolts and Titanium trans to engine bolts. Also have been running speedometer cable housing to trans main body aluminum bolts and a mixture of aluminum/Titanium trans cross member to chassis bolts and trans mount bolts.
I'm about to build an extra trans to have for a spare and will use a limited amount of titanium bolts on the inside. Maybe the tail shaft housing to main housing mounting bolts will be titanium.
If your not running full auto cut the park pawl gear teeth down to 1/4" thick. Then trim the main section just after the 1st governor seal ring groove. Eliminate the governor assy. Cut a new snap ring groove in the shaft and your done. You can get 1 lb out of the sun shell also.
