Loss of oil pressure

[C101971]

Hello all. So here's the story, I drove to work in the morning all was great. As well as most of the rest of the time since I have owned my truck. But a few times she's been fussy and I am really starting to wonder what is causing this. So on really really really hot days like today, it was 38°C, a bit too hot for me to want to drive my truck. 1971 GMC c15 with a 350. So it will start up fine, idol fine but after let's say 10-15 min she will bog real hard, I blamed it on vapour lock cause it's a mechanical fuel pump and it's 37 out. But since I got an oil pressure gauge I noticed the oil pressure will drop quite a bit once it bogs. Hard to say if there is a leak cause in regular temperature it will not leak but when it's this bloody hot it will leak a little oil, but not enough to cause concern. I checked the fuel lines and filter and no bubbling. If I let her sit in the shade for a while she will start back up fine. I've done road trips with her all day with no problem. If it happens and I'm go on the highway, within a few she will putter and kick back into happy mode and all will be fine.

Anyone have an explanation as to why the loss of oil pressure and bogging?