Superseded procurement regulations can be found by searching old Code of Federal Regulations (CFR). Older CFRs are available through HeinOnline. For the Federal Acquisition Regulation (FAR), search Title 48, Federal Acquisition Regulations System.
For historic regulations prior to 1984, be sure to search the correct title in the CFR. For example, the Armed Services Procurement Regulations (ASPR) were located in Title 32 of the CFR and the Federal Procurement Regulations (FPR) were located in Title 41.