Hey.
There is 30% seats reserved for BC in Tamil Nadu for NEET 2018. There are approximately 2900 seats for in all Government Medical Colleges under which 85% are under the state quota and rest 15% are under All India quota. Here is the cut off for BC category for all Government colleges in 2017 under the State quota.

ESI-PGIMSR, ESI Hospital,K.K Nagar,Chennai- 321
KanyaKumari Government Medical College- 330
Rajah Muthiah Medical College, Annamalainagar- 296
Coimbatore Medical College, Coimbatore -402
Government Dharmapuri Medical College, Dharmapuri-331
Government Vellore Medical College, Vellore- 351
Theni Government Medical College, Theni- 340
Thoothukudi Medical College, Thoothukudi- 326
K A P Viswanathan Government Medical College, Trichy -357
Tirunelveli Medical College,Tirunelveli-361
Thanjavur Medical College,Thanjavur- 378
Stanley Medical College, Chennai- 438
Madurai Medical College, Madurai- 401
Kilpauk Medical College, Chennai- 419
Madras Medical College, Chennai-477
Chengalpattu Medical College, Chengalpattu- 369
Government Thiruvannamalai Medical College, Thiruvannamalai- 319
Government Medical College & ESIC Hospital, Coimbatore, TamilNadu -339
Government Medical College, Pudukkottai, Tamil Nadu- 311
Government Medical College, Omandurar- 384
Government Villupuram Medical College, Villupuram- 326
Thiruvarur Govt. Medical College, Thiruvarur -317
Government Sivagangai Medical College, Sivaganga- 315
Best of luck!