What size fuses?

of course if you want to truly protect the car there is no reason in the world to fuse it higher than the functional/needed current of the existing system....

if i ran power cable rated to say 150 amps and the customer was only using one amp with a current draw of 75 amps i would normally always fuse the primary at 80 or slightly higher.... why fuse it at 150? if 100 will more than do?    when dealing with a potential dead short to ground i prefer to know that the fuse protection will kick in as fast as possible... a power cable will arc weld itself to the chassis before it blows a 300 amp fuse (keep in mind most ANL's are rated at 200% for 5 seconds)

Quite honestly, a dead short in the power wire will blow any fuse regardless of its value.  And it won't take long...

But I agree with using what's appropriate for the system being used..but with a caveat.  I run a 40 amp fuse in the main power wire in my car where if I fused to the value of the wire it should be 100 amps.  That was for the purpose of saving a few bucks and taking advantage of fuses that come 5 to a pack.  But I also know that I have to remember that the fuse value is lower than the wire value if I decide to upgrade my system later.  That's the caveat.