Transam461

Hello all, I am rebuilding a 455, and would like to know if anyone can tell me what oil pump that it has in it, going by the numbers off it. It has "USA" cast into it, it has the number "S42-203" cast into it, and on the bottom plate it has a number "43-203C" stamped into it. Have no history on the engine, but it has had several mods done to it, pocket ported C heads cut .020", ARP rocker studs, poly locks, Mondello 25-28 camshaft, Comp roller rockers, Speed Pro Pistons, Performer intake. I got the block all cleaned up today, and the 3 Center mains appear to have restrictors installed in the feed holes. It was in a 71 firebird that I bought, and the engine seemed to run pretty decent, didnt seem to be much of a tire burner, but pulled pretty good, but later found out the car only had 2.73 gears in it. I took it out and replaced it with a 455 Pontiac with a 4spd and 3.23 gears, and I wanted to freshen the olds 455 to use in something later, so here I am. Anyway, the oil pump seems to be in great working condition, I would just kinda like to know what I have, not sure if it is a standard volume, high volume, or whatever, but looks like the passage has been smoothed out through it. Can anyone help indentify what I have by going off the numbers that is on it? Thanks!

Brian