You may be right about some of your engine internals being a little soft.
You gave us the duration numbers on the cam but no lift numbers. Small blocks love good lift numbers - anything in the mid .550's & up.
I too have a 71 Runner with a small block, it's a .030 over 360 with 340 'J' heads. I have a Isky solid cam in the .550" lift plus I have 1.6 Harland Sharpe rockers for even more lift.
I too have the same 4 speed as you do and I only have 3:23's in mine but I do have a set of 3:55's to try.
I just finished my build but ran into a snag with one of the cylinder heads.
Anyway, the point I was trying to make was as others have said you don't need alot of hard core stuff to go pretty fast in the quarter.
Case in point - this is my buddies Aspen Drag car.
View attachment 1790690
All steel car - weighs in at 3800 lbs. front bumper lightened but the rear bumper is complete.
Full interior.
408 stroker engine (360 based) with Eddie heads.
Has a .590 solid Racer Brown roller cam.
Runs the smaller 904 transmission with a 4000 converter.
Best time = 10.90
He currently runs in the low 11's with it (11.25 in the rear quarter window in the photo).
When he had the original 360 in it - it ran in the high 11's
That engine wasn't stone stock, but wasn't too outrageous either.
Keep improving with what you have - you will learn alot and hopefully have fun while doing it.