It's interesting to compare the side shots of these heads.

Yours: http://www.ovtuners.org/gallery/headshots/IMG_0844

Mine: http://webpages.charter.net/muddybiker/R_Sport_2.JPG

Put them up in two windows and flip back and forth.

1) You can see how much metal has been shaved of the bottom of mine. I actually had to use some shorter pushrods, the 'normal' length SBC lifter tubular pushrods I had were too long, even with the adjusters backed all the way off. Of course, part of that is also the decking of the block and the lowered rocker shaft and different geometry of the roller rockers, but it appears that something close to 1/4 inch was taken of my head.

2) Intake ports have a lot of metal taken out of the top of the curve. The stock head hits the rough casting area and start to plunge downwards rather abruptly. The R-sport head continues farther back in a more gradual curve that leaves a lot of the valve guide hanging out in the open (the ends of the guide are ground down to smooth tapers).

3) You can see more of the exhaust valve through the R-sport ports. I wish I had take some pictures of the valve seat areas on my head when I had the valves out, that was the most dramatic change on the whole head compared to my stock F head. The F head kept on constricting past the valve seat, leaving a pretty small hole. The R-sport head was significantly roomier, and the roof of the port above the valve seat had a different shape.
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'63 PV544 rat rod, '93 Classic 245 + turbo