Where to get a front pump for a 42RH (A500)

Well, pressure does check out okay. The only gauge I could come up with only went to 200, so I didn't push the limits, but I hit around 160 with a little power braking, so I figured it was good.

The main reason I'm rebuilding the trans is because of some weird behavior that I'm trying to sort out. From my best guess I think the torque converter is randomly locking up when the truck is in gear (most noticeable at low speeds). For instance, as I was trying to pull it into the garage to start pulling things apart, every once in a while the truck would really tug at the brakes and the rpm would drop off enough to kill the engine sometimes (will sometimes even do it at stoplights). It's a 42RH trans, so it's hydraulically controlled, which I think should eliminate electronic issues from the equation. The torque converter was supposedly replaced back after we bought the truck around 10 years ago (converter was locked up when we bought the truck, took the trans to a shop). It does look fairly new now that I go the transmisison out (only put 40,000 miles or so on it since the rebuild), but I was considering replacing it. However, if the problem is in the trans and not the converter, I'd rather not drop the $100+ on a new converter. Any ideas where the to look for the problem? I bought a rebuild kit anyway because I think the clutches are probably pretty worn out, but I don't want to get the whole thing back together and find out nothing changed, especially since I spend 8 hours under the truck yesterday just trying to get the damn thing out.