i recently sold 2 boxes for that price. for $300 it would want to be rebuilt or at least inspected as good. thats the going price for 71b stumpys. your original price of $200 was closer to the mark for a 63a dogleg.

the x member would be specific to the x member boeing used in the car almost too. but a very good starting point for mounting the box in the car.

good luck- shame it didnt go ahead.