Numbers posted by CRB member Stan Clayton during June of 2007 therefore the numbers I suspect are from the year 2006. Add em up for what ever you want.

1060 SM
617 SRF
535 ITA
355 ITS
279 FV
268 ITB
197 ITE
189 VINTAGE
177 SSM
172 SRX7
155 ITC
141 EP + 243 National entries Jan-May = 384 total entries
141 FF
126 FC
123 SMT
121 IT7
111 FM
110 PRO-7
103 SPO
102 GT1
96 AS
83 F5
78 FA
77 SP
74 FP + 169 = 243
68 CF
60 DSR
60 S944
56 GT2
53 FE
52 ITR
50 SPU
48 GTL
47 GP + 75 = 122
46 CSR
45 GTA
44 FE
41 T1
39 GT3
39 SSB
39 SSC
38 S2
38 T2
36 CFC
35 T3
32 FST
25 CFF
23 ITX
21 NCF
20 CC
19 GTP
18 RS
15 BP
13 PCA2
12 PCA1
9 FSR
9 PCA3
9 ST
9 FB
6 ASR
6 ITM
5 DP
5 SPM
4 SRS
3 ITT
3 SF
2 BG
2 CP1
2 HC
2 SG-2
1 ITU
0 HP + 112