HEY BOB
If you don't want to mess with your valve covers, especially since they were not made to have holes in them, Why not just get new oil fill tube with push on BREATHER CAP, their only like $15, and have a fitting welded on for your existing PCV to screw into?? Then just paint it black. I wouldn't mess with stock covers anyway.

 

The one thing I can see happening if you have a breather and PCV valve in the oil fill tube, is you'll most likely be sucking oil through the PCV since the breather above would be the only source for the crankcase to breathe in and out. I'd hate to put a hole in your nifty scripted valve covers too, but since the rear draft vent is non-existent, that's the logical place to have a breather or PCV valve. Another option would be to put the hole for the PCV in the back of the valve cover, to keep it more hidden and off the top, then use a push-in breather type tube. Just be sure to measure carefully for rocker clearance.

 

I believe that putting a vent-cap on the filler tube, so close to (as in just above) the PCV valve, would simply let the PCV valve suck air through the vent-cap, thereby negating any purging of the crankcase blow-by fumes, which would then continue to accumulate in there (outcome unknown).

What I did do today was to install a PCV breather filter inside the air cleaner (inside the main filter area), and then connected a PCV hose from that small filter to a 90-degree fitting that goes into a grommet I'd installed on the top rear of my right-hand side valve cover. I placed the hole for this grommet between two pairs of rocker arms, so that there is at least no oil being sprayed directly at the grommet opening. Because the grommet and hose are partially hidden beneath the four spark plug wires routed above it, you have to look to notice it.

Upon testing this set-up, I found that the hose going to the air cleaner (for a fresh air source) indeed has adequate suction, and there is no longer any vacuum build-up in the crankcase ( as was scarily evidenced before by removing the solid filler cap and hearing/feeling a strong vacuum sound).

Although only time (and more mileage) will tell, a 10-mile test drive today, up on the freeway and on surface streets, showed no signs so far of any oil being forced up this tube and through the small filter into the carb intake area, nor any signs of oil being burned out the back. Rather, the system actually seemed to be working and therefore effectively drawing crankcase fumes from the rear up to the PCV Valve... just as nature intended.

 

Good deal, "just as nature intended", or engineers at the very least! heh heh

 

Well I have to say I've learned a lot from this thread. Very informational.