Your proposed wheel/tire combo is pushing the limits, but should work, provided you order the wheels with the proper backspacing/offset. We've seen 275/35-18s on the front of fourth-gens before, so that shouldn't be a problem, though they're usually mounted on a 9-inch wheel. Still, if you're determined to have a 9.5-incher, sources say it can be made to fit. The 10.5-inch rear wheel is also on the edge-a 10-inch rear wheel is more common for upgraded F-cars of this vintage, but again, sources say it should fit, though depending on the wheel manufacturer, that 315/30 tire may be stretched a bit to span the rim width. Definitely consult with the wheel-maker prior to ordering. Some fourth-gen Camaro SS owners like to use 11-inch ZR1 wheels on the rear of their cars, but if you've ever seen this, you know that they usually hang out under the wheel lip, and even a touch beyond it in some cases (usually with 335/30 tires). That said, it's a safe bet that you won't get 12-inch wheels in there. Since you have the Hotchkis suspension with its rigid trailing arms and panhard bar along with stiff urethane bushings, you can afford to run the rubber fairly close to the inner fenderwells (you need a minimum of 11/42-31/44 inch of clearance at rest), but if you were still running the stock stamped-steel/rubber pieces, the flex would require more clearance, and therefore would likely not permit the use of a 10-inch wheel or bigger.
By the way, fourth-gen F-cars that left the factory with 17-inch wheels have a spacer between the rubber jounce bumper and the frame over the rear axle. Your car should already have these (and you may be able to spot them by looking through the wheel openings), but for those upgrading from 16-inch rollers, these should probably be added to limit the axle travel, providing a bit of insurance between the tires and quarter-panels. You can get them from SLP.
Oldsmo-BuickI am planning on rebuilding my Olds 425, which is out of a '65 98. I want to bore it 0.030 over, and I am trying to decide on pistons. My question is, will 0.030-over Olds 455 pistons work for me? I am almost positive that the 425 and 455 share the same block. I am planning on putting this motor in my '69 Buick Skylark along with a TH400 trans. I know it will be tough to do, considering I will need a new trans crossmember and the Olds block sits an inch higher than a Buick big-block would. But time is not a concern for a 19-year-old college guy who is sick of my generation driving Kia Rios mod'ed with aluminum wings and coffee cans for mufflers. Any advice you can give me is great.John Gerrity Mokena, IL
The 425 and the 455 Olds do use basically the same block-that is, both engines use a 4.125-inch bore and 3-inch main journals. However, if you check into the factory specs a little deeper, you'll find that the 425 uses 6.998-inch connecting rods while the 455 uses 6.735-inch rods, and the stock pistons in a 425 have a 1.615-inch compression height while the 455 pistons have a 1.74-inch compression height. So, pistons are not interchangeable between engines.