Ok, I was bored at work: Cactus Classic breakdown of 364 current entries as of February (the last posted list on SRS's website)
2wd stock = 44
2wd 19T = 50
2wd mod = 70
4wd mod = 87
Trk 19T = 29
Trk stock = 27
Trk mod = 40
40+stktrk = 17
Looks like we got about 38 heats.