LR Fastners (advertised in the magazines) produce kits for various parts of the vehicle. I have recently recieved their full 109 body fastner kit, plus a few specified extras. The kit is huge, and has every nut, bolt, rivet, washer and bracket for al sorts of variants, including spares to allow for the inevitable dropped nut or lock washer. He packs the whole kit into small sealed palstic bags for each individual job (eg. 1 for brake pedal box, another for clutch pedal box), with the sealed bags being grouped into vehicle regions within the pack (eg. bulkead, rear tub mounting, roof mounting, doors, etc.)
He's not cheap, but it all sems top quality, and I hate to imagine how much time he spends (and thus saves customers) counting, separating, packaging and labeling each measure of fastners. Worth every penny.
When assembling, use a smear of copper-ease onthe bolts, and once finished, give them all a quick spray with some waxoil. That way, you'll have the correct spec fastner (size and strength), protected for eternity by a coating that inhibits galvanic corrosion, rather than accelerating it.