Here is the REST of the story.
We checked all the available locks and it seemed to me the important dimension is the pan to the sear bar, since I am replacing an old lock and these dimensions are pretty much set. The lock we decided on was Chambers Small Siler. It's almost a perfect fit except for the plate dimensions. So after much consideration here's what I'm going to do.
The stock being maple with some spaulting became part of the solution. The inside of the of the lock mortise and edges is very discolored and stained, the rifle is about 50 years old by our calculations. We've already replaced the barrel recently the original was badly pitted but he didn't know that. After the new barrel he was still getting numerous misfires because of the loosey goosey worn out Russ Hamm lock. Sometimes it sparked well sometimes not. The frizzes wobbled and the flint sat against the frizzen at half cock and the springs were weak. It had seen better days.
I've decided to plane off the lock panel down to the level of the old lock plate and replace that wood with some closely matching curly maple. Then re-inlet the new lock, stain and finish to match the rifle. I figured any glue seam line that may/will show should be camouflaged by the spaulting lines.
He's going to have the Oldest new rifle on the block or is it Newest old rifle.
