Just to correct a potential misunderstanding, if you have undersized wires or corroded or loose connections or a bad ground, you might melt something (in an extreme case) but you will not blow a fuse.    In the case of headlights, they will be dim because part of the available power will be sucked up by the non-headlight resistance so there is less left over for the headlights to glow.

The total current draw of a worn circuit is in fact lower than the identical new circuit, so you won't blow a fuse that way.

tabe johnson/87 westy (ex)