I like Jim at RB and ran pretty well w/ an ST-21 in my 440. But those are some OLD grinds, and cam lobes have evolved dramatically in the decades since those masters were hand-designed.

The biggest difference, IMO, is valve train stability at high(er) RPM. When I dynoed three different cams (two UltraDyne .904" SFT and the ST-21), the UltraDynes would rev cleanly to about 6800, even though that was well past the HP peak. The Racer Brown, on the other hand, went into total valve train crash about 6400-6500. On the the track, if I was running my 28" tall tires insted of my 29", the shorter tires would put the engine right up into the valve float at peak RPM and the car would just freakin' stop accelerating. If I ran the 29" tires, the taller tires kept the RPM down enough to keep from having to rev that high and it would pull about 2 MPH more.

This was using ported OEM heads w/ 3/8"-stem 2.14" x 1.81" valves and valve springs having about 140#s closed and 380# open pressure, so it wasn't a lack of spring load. The dynamics are simply crude in comparison by virtue of how long ago they were designed.