4awg wire can handle up to about 125 amps. So use any fuse lower than that. I think you'll need to go to an ANL fuse holder as the largest commonly available AGU fuse is 60 amps, with some 80 amps around (not common).

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2004 300M SPECIAL
Alpine CDA 9833
Alpine Pxa-h701
Alpine Rux-c701
Rockford fosgate p400-4
Rockford fosgate p4004
Hifonics BX 1205D
JBL c608 GTi
JBL p963
Infinity 2.5" center channel
Alpine type R 12"(2)
200 amp alternator
yellow top battery
0 awg power and ground (welding cable) 300 amp anl fuse
all active SQL set up with 2000 watts rms