I'm not sure which, if not all, vendors handle the gauges you are looking for. However, since most come from the same place/manufacturer I shop around. For me, I have found the Truck Shop to have the best assortment, and prices, on a lot of gauges. I've not had any problems with my 12v gauges fitting in my 52 panel.
$58 here.
http://www.truckandcarshop.com/trucks47_59/t47_029.html$95 here
http://www.oldchevytrucks.com/cart/index.asp?cat2=10706&path=1947+%2D+Early+1955+Truck+Parts%2FSpeedometer+%26+Gauge+Items%2FGauges%2FFuel+Gauge
I've been running TRUCK SHOP gauge for three years. No problem.
