Late cars with the ribbed oil pan use a different pump than the early cars. I think the early ones use a 108 ( PN ) pump and the later ones use a 114 pump.
Early pumps usually have one bracket and I think the late ones have two. They also have an extra oil pressure relief valve on the pump while the early ones don't. This late pump can only be used with the late ribbed oil pan. If you use this pump on an early engine the rubber baffle at the bottom of the pump will be crushed against the bottom of the pan. The late pan is slightly deeper by about 7 - 8 mm which allows clearance for the new style pump.
I imagine you can use the early pump in a late engine ( you should use the right one of course ) but you can't use the late pump in the early engine. In both cases, each engine has an oil pressure relief valve on the end of the main oil galley at the front which drains into the chain case.
Although the gage may read 35 PSI at full peg, the pump will deliver much more than that and well over 100 PSI when the engine is really cold. I think the OPRV is set to open at or about 90 PSI. Hot running pressure is usually 60 -75 PSI on fresh engines. I wouldn't drive one with less than full peg at road speed.
So, you have the early pump in all likelyhood. If you have any questions about the pump's condition, get a new one.
Pumps are several hundred dollars so make sure it needs to be replaced. I never take pumps apart as a rule unless they're made of unobtainium and I have no other options. Most builders, including myself, will not warranty a rebuild unless it has a new pump. Some even insist upon a new water pump as well.
