Old school talents required here
RocketBob sez: "According to the RV-4 plans all four splice plates are exactly the same and symmetrical."
Well, that would be nice. In the real world, it's not really probable that such would happen using any sort of hand drilling procedure. Some machining techniques can't get it right either! That's why oversize bolts are available.
BTW the F1 plates are NOT completely interchangeable; the lower plates are chamfered along their lower edges. Your plates may end up the same way for bulkhead flange clearance. After drilling, carefully mark the plates' positioning (top, lower, front, this side fwd, etc). All this in in the F1 manual, even tho the hole positioning on those parts is as close as possible using modern machining techniques. Once reamed to fit the spars per the manual, the parts are locked into that orientation; they do not interchange.
As usual, be careful what you read on the internet.
If you drill the plates to exactly match the current plates, which probably don't match each other to start with, you will re-order the parts and start over again, or go with the very expensive oversize bolts. Ugh.
So, you will likely drill the parts up using the early RV type setup where you set the spars up on sawhorses, with the drilled plates on top (pinned), and proceed to drill the clamped lower plates one hole at a time, using the drilled plates and the spars themselves as the drill template. Drill bushings will help greatly, but since the holes are not likely to be perfect 90 deg holes, simply setting things up and going after it with .374 & .249 drill bits would not be my recommendation.
If you need further info, send me a PM. Hole exact placement is less important than getting the holes round, and the correct size. Think 'tractor', not 'space shuttle'.
Carry on!
Mark