I'm in your boat! I bought a 1957 (really a '56) on ebay and dis-assembled it. It was original but with Vacuum wipers. I also have a 544 that I re-wired last year in anticipation of this conversion to a new body. To begin with, the 544 never stopped being on the road. Nice concept but also meaning any breaks in any component needed to be working the next day. So, alot of splices and double wires when something didn't work. My solution was a complete rewire beginning with a NAPA fuse box with "blade" fuses and I mounted it on the rear deck under the rear window. Then I made a plate to hold my switches (6)located under the radio and ran wires from the fuse box to the plate and to the component. I ran individual grounds too so I didn't need to deal with that issue. Really not too difficult when approached in a simple way. No relays, Just wires! Fuse for (coil) ignition, one for Driving lights one for High beams, another circuit for wipers and one for heater. Electric fuel pump and overdrive on the same circuit. Bring the power from the fuse box to the "on-off" swich at the plate, on to the place you want the power to go. Sure I need to time the wipers so they are off in the "down" position but with practice ...Plus I now have all new everything! All wires and switches are new. Switches are just on-off and from any hardware store. I.E. replaceable with very common items.
Below is a basic code

6 Brake Light White Black
24 Brake Light Power Black Black
9 Fan Ground Yellow Black
8 Fan Power Yellow White
25 Fuel Pump Blue
5 Gas Tank Sender White White
1 Head Lights Blue Green
3 Headlights Bright Blue Black
2 Headlights Ground Blue White
18 Heater Power Green Black
7 Ignition Yellow Green
17 Ignition Power Green White
26 OverDrive Green
13 Power From Starter Pink Dbl Green
14 Power From Starter Pink Dbl White
15 Power From Starter Pink Dbl Black
23 Radio Power Black White
19 Starter Button Red Green
22 Starter Button Power Black Green
4 Taillights Driving White Green
11 Turn Left Front Orange White
10 Turn Right Front Orange Green
16 Turnsignal Power Green Green
12 Turnsignals Ground Orange Black
20 Void Red White
21 Void Red Black

Once I was told that electrical work is just like plumbing. "no leaks"

Christopher