Why dont you try pricing your parts out simply by using the internet for pricing . For the belts/hoses/battery etc , just go to Napa . Maybe for your harness why re-wire ? Try using someone like Rhode Island Wiring for pricing , you would probably end up happier in the long run anyway as would be more period correct , just grab some screen shots im sure that would suffice . As far as your quote for the labor ( 1300.00 ) that would seem fine if that was for mechanical labor only as most mech labor rates are in the 75 - 100 area . Most shops i've dealt with as far as labor goes your probably in the 8 - 10 hrs just for the harness not incl the other under hood items belts etc . Keep in mind very few ins co's have specialized antique appraisers so the guy may not have ever looked at a car 60's let alone the 50's.If these suggestions dont strike your fancy try using a independent appraisal co as they would give you a fair 3rd party accessment , as the shops estimate ....we'll im sure if they could would be on the opposite scale of the ins co . Good luck with your situation !