The critical criteria for Classic is moments, spans, shapes, areas and air foils. Engine size does not matter. Guys have been stuffing ST.46's into Nobler's for Classic for a long time and the AeroTiger .36 is a favorite for Classic models if you can come up with one. I would try and keep all the original cowling shapes just because that's what you built back then, and alloances can be made for mufflers and any slight changes to accommodate a muffler is understandable. Covering and finishing is up to you also, but if I were you I would try and replicate that and in the spot where your dear Grandmother inserted her hand, I would put the sentiment, "In Loving Memory of my Grandma, (insert name here.) It's an interesting story and part of your history and the model's history and will make for some interesting chit chat at the flying field. As for landing gear, build it with the grass gear and make up the pavement gear and keep looking for photos. I think you will find that the model and it's vback story will be well received in Tucson next year.
Good luck and have fun,
Dan McEntee