1979 F150 4x4 400-possible oil pressure issues, carb issue

Hello to all-
I have an issue-I finally got my 1979 4x4 f150 highboy home from my dad's place. We had the engine replaced 14 years ago, when he first bought it as a plow/hunt/work truck. The truck has served us well, seeing around maybe 3,000 or so miles a year; now that I have the beast, and I have started driving it on a regular basis I have noticed a few problems.
First is the oil pressure issue that is severely worrying me. The engine has never given us problems, but after driving it the last two weeks, the guage is riding it out on the bottom of "Normal" and occasioanlly drops below stopped at a light. I know that the old ford guages are not the most accurate pieces, maybe it's a clogged sender, but still...no noises are coming from the engine, runs down the highway good, even with 4.10 gears. Oil is 10W30, buy my dad has been running bargin oil filters and not FL-1A's like I use. Oil usage is very minor, mileage is at about 63k on the rebuilt engine.
Thoughts?
Other issue is a bad stumbling when I take off, I am assuming the carb is due for a rebuild, but I have a torker intake and a 600cfm Edelbrock performer carb. Is 600cfm big enough for a 400? Motor is stock, not built. Been through the fuel system, new filters, fuel pump ok.
I also got a holley projection commander 950 efi system from a freind, but leary of using it. It is an older system that was on a 460, and sounded very nice, but that engine was built. does not have a lap top hook up, old box with knobs for adjustment.
thanks
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Easy way to check the oil pressure issue is to buy a more accurate gauge and install it, they're not that expensive considering what you're monitoring.

I'd go with that 600 cfm carb, on a stock 400 it should be just fine. Its tough to beat parts you already have, but don't forget to check the timing and make sure the advance isn't stuck.
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Thanks...I am not the greatest at figuring things at times. I can build a car from parts from scratch, but it's that fine tuning part that always screws me up.
As an odd note, I was working on installing a new radio, and I had to move the cluster some, and now the guage is reading a little higheer up as I drive. I thik it's time to replace some guages.
I appreciate the help
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