Hi, I'm going to be building my 70 Skylark this summer. My plans are: HEI, ta310 cam, head porting, .02 head decking, and steel shim head gasket and shift kit. Along with this I am planing to change to a posi. The Skylark is originally a 350 2 barrell, so it has a 8.2 2.56? And I'm going to convert to an 8.5 10 bolt for durabiaty, and according to buickperformance.com. parts are more popular and cheaper. The 8.5 housing and axles I am planning on getting is from my friends 1969 Pontiac GTO 400. He told me it is a open rear with 2.73? gears. For $150. First question. Will everything bolt right up to my Lark other than the driveshaft having to be shortened about 1.5"? I looked around at carriers for it, and the Auburn Posi Unit 10 bolt 8 1/2" GM looked most appealing. $359. Would it be alright? I'm looking into getting 3.73 gears. But I don't know which type of gear I have to look for, from what manufactuer? Other than that, what would be the difficulty of installing this, and what other parts would I need? And what possible issue's may arise. I know this is a lot of questions, but I am totally new to this and any help would be appreciated. Thanks
Unless the '69 GTO has been converted to an 8.5 rearend, it will have its original Pontiac 8.2 rearend. 2.78 was a common Pontiac 8.2 ratio. Might look the rearend over. Stock Pontiac 8.2 rears had only one access hole in the axle flange. If the propperly fitting rear in the GTO has staps & 7/16" headed bolts holding the u-joint to the pinion flange, then an 8.5 A-body rear has been swapped in. All 8.2's used U-bolts & nuts. If the GTO is now equipped with an 8.5 A-body rear, the stock GTO driveshaft will have been shortened 7/8-1 1/8" (1.5" is too much). Stock turbo 400 '68-72 GTO driveshaft measures 55.375" on the u-joint centers. '68-70 4 spd GTO drive shaft measures 60.00" center to center on the u-joints. Aftermarket 8.5 posi's. Build with the easily rebuildable Eaton clutch type posi's all the time, & prefer them for most applications. Over the years, have also built quite a few r/e's with the std cone type Auburns & even more with the Pro series cone type Auburns. For years, the Auburn pro series carrier was the only aftermarket choice for the "BOP" 8.2 & the Pro series carriers I've built with seem to have held up well. New gears... US Gear-Strange or US Gear Torqueline is the ticket. No reason to settle for noisy Richmonds. Am no longer using 8.5 Motives either. Good luck on your summer build. :3gears: Roger
