IMHO, You need to run a subpanel off your main panel.
Hopefully, you are using a 50amp Astron for the radio since it can pull 45.6amps on SSB. A 50amp Astron needs 8.2A @ 120v full load. Your 150A Fatboy 14.5v PS goes up to 15.5v@150A = 2325w so figuring in inefficiencies, you will want at least 3000w available for it. So a 25A or 30A 120v breaker for the Fatboy and at least a 10A 120v for the Astron. Figure on 30A @ 120v per hot to be on the safe side. 100' @ 30A @120v = 6 gauge copper or 4 gauge Aluminum (3% v. drop). Code requires a 4 conductor feed, the ground can be smaller, so 100' of 4-4-4-6 Aluminum should do the trick. You'll have to buy a ground buss for the Subpanel because they don't come with one (go figure). Also put the 25/30A and 10A breakers side by side in the subpanel so they are on different hot feeds. Use a 30A DP breaker in the Main panel to feed.
NOTE: if the 8 pill is a class C, there is a good chance that 150A@14.5v isn't enough. If that is the case, you will need to put a High Output battery in line with the DC. A LTO battery @14.4v (6 x 2.4v cells in series) would give you the response that you need to handle SSB peaks. A 16v 500F super capacitor will also handle the SSB peaks.