Technical Electrical help

Got a 55 lincoln that the person before hacked up the wires in. how any circuits can I get away with for a wire harness to run power windows power wiper Motor and electric fuel pump along enough to run automatic doors. It does not have air or heat but has turn signals. I was looking at 21 but don't think I need that many.
Any help?

 

Too many circuits would be better than not enough.

 

You might be better served by finding out how the circuits are labeled on the fuse panel to make the decision on which to buy. Some are labeled on panel, others on cover. Misnamed circuits will be confusing forever.

 

One issue with older cars is the OEM didn't put everything in the fuse panel; optional 'extras' like power windows and AC used inline fusing or circuit breakers. Figure on a separate circuit for each subsystem; power windows, wipers, electric fuel pump, head/tail/brake/turn lights (one circuit for each), etc, etc... Make sure each circuit is large enough for the connected load by sizing them at 125% of the 'running current', if a electric motor is involved go 150%. If you're installing new aftermarket components, use the recommended fuse size and size the circuit accordingly. Too big is always better than too small.

Electrical is one place you don't want to cut corners...

 

Just to repeat, too big relates to wire size and number of circuits, not fuse amperage.

 

Just be aware that some older Fords (like mine) had no fuse block at all, just in-line fuse holders. I don't know how far that spilled over into the Mercs and Lincolns. You need to find a schematic for your car before going off the deep end.