The last guy who owned this 72 RoadRunner removed the fusible link completely and ran a straigh wire to the circuits. I am looking in the FSM and the Fusible link is rated at 60amps. I am assuming its this required value because the alternator was rated at 60amps. I have swapped out to a single wire 140amp PowerMaster...Is the 60 amp fusible link still required? Can I run a 40amp ATO style fuse...the only other one I have is 60amp MAXI fuse

You should still use the factory gauge fusible link which is 16ga...regardless of the alternator output. The fusible link is there to protect all the wiring in your car (especially the well-known ammeter) from melting down due to a prolonged high charge/discharge situation. This would be something like a melted/shorted wire. Also since the rest of the wiring in the car (assuming stock here) is only rated for so many amps, I wouldn't 'up' the link size as it wouldn't adequately protect the wiring from burning up. If you are adding additional electrical loads (WP/fuel pump/fans/etc), pull them directly from the alternator stud which will in effect, bypass all the wiring when the car is running.

Yeah, you could use a standard fuse but it will blow almost immediately if there is a short spike on the charging circuit which WILL most likely happen and shouldn't be cause for concern aka right after cranking for a while and trying to recharge a depleted battery.

There is a reason the factory didn't use standard fuses...

I could see maybe getting a higher rated fuse (75 amp+) and putting that in-line with the fusible link as a secondary fuse but I don't really see a significant benefit here. The factory knew that these cars would have short term hi-current draws that couldn't be sustained for the long term but were a fact...that's why they used the fusible link.

Agree replace the stock link with a stock size link. With a 140A alternator, hopefully you are not passing charge current through any factory wiring (probably 12 gauge!). 6 gauge wire from the alternator output stud to fender relay or battery with 10 gauge fusible link or 150+ amp slow blow fuse would be ideal. 8 gauge would work.

I use a 70 amp style fuse that replace the fuseable link. This is like he newer cars have that does replace the older wire harness fuseable link. The fuse is plastic and comes with eyelet terminals on both ends. So I bolted it to the battery cable and bolted the other end to the eyelet terminal on the wire harness I installed. It has worked good since 2006. My alt is a 60 amp unit. Ron