Two part question, Well after driving my challenger since 1982 the drivers side frame is rotted were it bolts to the K frame rear. There is rot also by the battery tray and in front of the hinge. So do I replace the rail and the inside splash shield ( or whatever it is called) or just the rail or get a cap. Who makes the best replacement parts? Also I live in Virginia tidewater area. This is something I cant do, any recommendations for a Va. shop that specializes in mopars? Thanks in advance!

Look close at the rail. It may be a mouse nest that rotted only a small area. I fixed 2 spots on my 64. The rest of the rail doesnt even have any scale inside. Easy fix if it's a small area
Doug

Like he said look very close a the rail.

My Hardtop challenger had the battery explode and drain acid in to the frame. It was rotted front to back.

Personally I do not like the caps but they are something almost anyone can do.
I do not care for them because most of the time they do not address the original rust issue. It will come back to haunt you later and the repair is obvious.

The splash shield is usually called the inner fender.

If there is rust through in front of the hinges only, they make repair patches for that but since the battery tray area always rusts it may be better to replace it all.

Got any pictures?

Well, one of the Mopar hobby's foremost restoration guys is right up the road from you in Richmond. http://www.rogergibsonautorestoration.com/Frank/Frank-Badalson-About-Us/

Or, contact this shop directly. Stuart Jackson does the body work for all of Badelson's restorations. Not far from Richmond. I've seen his work, it is top notch. https://www.yellowpages.com/burkeville-va/mip/stuart-jackson-restorations-inc-5406628

One more. Clark Classic Restorations. They specialize in Mopar restorations. They are in Greenville, NC, not too far from Tidewater Va. I have had work done here. It is outstanding. Any of these shops would treat you right. https://clarkclassic.com/

Thanks for the leads!!

I'm not understanding why you feel using a cap doesn't address the problem. When installing a cap as per directions you cut off most of orig rail. Unless top of the rail is rotted bad part is cut off.