Hi Bill,
Not sure if I can help, but I'll give it a shot.
I looked at the drawings you listed, and I would agree that they leave a little to be desired in this area. Looks like the W-408-L & R ribs are slightly undersized to allow for the W-423 splice plate that wraps around the leading edge for the outboard end of the tank to attach to. From what I can tell, the rib flanges point outboard, and the web is located at rib station 55.75. There does appear to be an angle re-inforcement just inboard of the rib's web, and is riveted to the web, and bolted to the spar through the cap strips (or flange strips). I looked at some old photos I had (not digital unfortunately) and one of them seemed to verify this re-inforcement angle was on the INBD side of the web, but unfortunately, I don't have a close-up photo of exactly what we need to see.
In DWG 12, there's also another angle shown (just outboard of the W-408 rib) on the forward face of the spar between the upper and lower cap strips, it's riveted to the spar web with some AN470AD4-5 rivets, but it's not clear to me if it gets riveted to the W-408 rib. I don't think it does because it is located 1/2 inch too far OUTBD for the vertical leg of the angle to attach to the web of the rib on the OUTBD side. I also think it would not line up well with the angle on the INBD side since one sits on the spar WEB (OUTBD angle), and the other sits on the cap strips (INBD angle), so they couldn't both attach to the web from either side and at the same time, share common rivet holes. I'm not sure what the angle on the forward face at rib station 56.25 is there for unless it just provides spacing between the upper & lower cap strips.
That area of my wings has been closed-up for a while or I'd try to look at the way I built it to see exactly how it went together. Unfortunately, my rememberer is broken. Good luck, I hope I helped some.
Les
RV-4
S/N 4030