Most of the body and chassis fasteners will be metric, common thread pitches too. Order bolts from Mcmaster.com as they have pretty good prices and most sizes will be sold in boxes of 25, 50, 100 etc. S.S. bolts should have a small dab of copper anti seize. Most of the bolts on an XJ areM5x0.7, M6x1.0, M8 x 1.25 and M10 x 1.5. The engine should be SAE for most but accessory mounting not attached to the engine its self will be metric. McMaster also sells killer coated bolts that will hold up well and are graded in 10.8 and 12.8 for suspension and axle attachment.