Update:
Was finally able to spend some time on the truck and got a resolution to this issue.
I decided to drill out and tap an M8 nut to see if how it went before I tried it on the on the tank nut and afterwards I opted not to go this route. The new 1/8 NPT threads appeared to cut deep enough to make good threads in the drilled out nut but once the larger tapered part of the tap got into the nut the going got very tough, even with cutting oil. I had the nut secured in a vise and one time the tap twisted the nut right out of the vise. The thought occured to me that the tap could break the tank nut loose in the same manner so I punted.
With this in mind I went the route of using the top feed sender. I'm glad to report that the glass bowl type fuel pump had no problem at all pulling gas up and out of the tank, through a new 2' long dry gas line and on to the secondary filter and into the carb. Since the carbs fuel bowl was full it started right up and the glass bowl fuel pump immediately filled w/gas. This is good in that I had removed the bowl to clean it which had emptied it.
I ran the truck a good hr around my local highways and byways and I didn't have any fuel related problems.
I had a few other unrelated problems creep up but they are for another thread.
I do need to add that the M8 plug on the bottom of the new tank leaked on my overnight leak test.When I pulled it the teflon tape was nearly all useless. So I used some aviation permatex on the threads and between the flat washer and tank and this seems to have fixed that. I'm glad I decided to do the leak test w/the tank out of the truck. I've pulled the tank in this truck 4 times now and was getting tired of soing that
I've probably drained and discarded 8 gals of gas!
So in closing, the nearly new glass bowl fuel pump that is spec'ed for bottom feed gas tanks doesn't seem to have any problems pulling fuel from a tank via the later model top feed fuel sender. I'll update if it does fail if I think about it. This old truck will be getting alot more weekend usage as I get all the bugs worked out.
Dave
