Yes, they're pretty good. Classic Records managed a pretty balanced frequency response even in the 33 rpm issues.
These are also quite good sonically, if not quite up to the standard of the Hendl recording:
LSC 2435 - Sibelius Violin Concerto
LSC 2652 - Bruch Violin Concerto
LSC 1903 - Brahms Violin Concerto
.
"Can anyone offer input on the RCA Heifitz recordings on Classic records?"The best of the bunch sonically, for me, is the Hendl Violin Concerto on LSC 2734 - really superb!
These are also quite good sonically, if not quite up to the standard of the Hendl recording:
LSC 2435 - Sibelius Violin Concerto
LSC 2652 - Bruch Violin Concerto
LSC 1903 - Brahms Violin Concerto
.