With U.S-made cylinder heads used on Panteras, two-piece welded valves have multiple grooves and matching split keepers. Even cheap aftermarket stainless steel valves may be welded from two pieces. Good, one-piece valves have a single wider groove and matching keepers. Some two-piece multi-groove exhaust valves have magnetic stems but the welded-on heads are not magnetic (or not near as much as the stems). The problem with welded valves is when engine revs exceed maybe 6000 for any reason, the weld between valve head and stem may break and the welded valves become two pieces again. The muligroove keepers also do not hold the stems tight. Breakage of a single valve (or a keeper letting go) normally destroys the entire engine in a heartbeat.
Aussie-cast blocks are reported to have a smaller diameter hole for their smaller OD distributor shaft; this means that U.S-made distributors (stock or after-market) will not drop in place without drilling out the block's hole first. There are other minor detail differences.