By Matt Hladik The punishments meted out by NASCAR to RFK Racing’s No. 6 Ford Team and driver Brad Keselowski have been upheld. The National Motorsports Appeals Panel ruled on Thursday that the penalties will stand. RFK Racing was found to have violated Sections 14.1 and 14.5 of the NASCAR Rule Book. Keselowski’s team had been hit with a sizable penalty in late March for illegally modifying a part for their Next-Gen car. “NASCAR competition officials handed down an L2-grade penalty March 24 after an inspection of RFK’s No. 6 Ford at its Research & Development Center after the previous weekend’…