Raften , since you are bringing in to a welding shop also have them inspect the upper front spring perches . I don't know how many years it covered but for my 94 there was a recall and they were rewelded by the dealer , which would also imply that it's OK to weld on the frame .
FWIW , the body shop down the road had a 2nd gen dodge 3500 for a wrecker and the rear frame was all double plated , he said the dodges needed it for heavy duty use .
I did similar to my 94 after it developed a crack between the rear spring perches on one side and between the cab and spring on the other.
Not to discourage you , a GOOD welder can make it all better . Good luck .