Mr Orander, since you signed in as a "guest", I'm thinking you might be the "mechanic". First of all, thanks on behalf of Willys Jeep owners that you are even willing to work on non-computerized vehicles, a scarce commodity these days. Second, as Mr Pilot said, no one means anything negative to anyone, we're just sharing experiences in seeking solutions AND "learning from others from that".
Suggestion... if you are planning on "replacing the fuel lines" and "relocating the pump and changing fittings", have you and the owner considered retaining the existing line to be used as a "return line" from a "pressure regulator"? It seems from shared comments that Solex carbs are "touchy" about wanting low pressure. Seems like an opportunity to utilize the lines there and approach that potential issue. Have "temperatures" at the pump (and carb) been monitored to see if it might be a "source of the heated fuel" potential issue?
These are just suggestions of how "I" would approach the issue if this situation were mine. This site's "sharing of knowledge and experiences" has saved me lots of time and expenses over the years. I am grateful to "all" who participate. It has been very helpful. Good Luck, and please keep us posted of trials and tribulations. Thanks.