Alternative alternators

[morris]

I've been looking at alternatives to the current arrangement of my alternator being down on the off side of the engine next to the exhaust. You can buy small 60A alternators that should fit in the correct place on the M50 engine and then allow me to have a proper belt tensioner rather than my current best guess fixed tension.

http://www.racemettleltd.co.uk/alt.html

There's a helpful formula at the link above that tells you what output you need. I've been round the car working out the power draw on various components but the ones I'm not sure on are

Horns
Fan
fuel pumps
Engine ignition, injection and ECU.

I know what fuses I have fitted but these will be typically much higher than the normal power draw.

Does anyone have any ideas, especially the engine?