I would do a stock bluebird rebuild with better bearings, vet head gasket and arp hardware as that will handle all the disco can throw at it unless you plan on over boosting it. Save the money fo...
That's why you can just convert a B15 6spd that already has the LSD or do like me (which may cost more) and get a P12 and swap the stacks and diff assy.
I have used Opticoat multiple times in the past for this, as it is one of the products suggested uses, but I've found that it doesn't last more than 6 months or so. I don't believe the product has...