It's interesting that he's an independent, yet underwrote the estimate. Independent's get paid for writing the estimate, and that's it. If there's a supplement, they have to take care of it on their own dime. Usually, it's "write it high and let it fly" with an Independent.

That said, he likely wrote it at $52/hour because you don't know where you're getting the car fixed. If he's someone who regularly works for a collector company, he knows that a resto shop will charge higher rates, and he'll make the adjustment once the car is in the shop. Collector companies don't stay in business by arguing with their customers' repair shops. Pick a resto shop with a reputation for quality, and get the ball rolling. You're not going to get collision repair timeliness with a resto shop. Resto shops aren't production shops.