I prefer the solid state diode battery isolator myself.
The relay alone should work fine.
Sadly, there are plenty of alternators out there that are not well suited for charging a partially discharged batteries. They'll have the capacity to charge it while driving around, but may provide little more than the car needs to run when turned at idle RPM. More of a problem is they're not very reliable when used for delivering high currents. Case in point, Motorcraft 2G alternators used in older Fords. They didn't even put an output stud bolt on it, just used a plastic housing with 3 flag connectors. Yes you plug it in. They can, and will, physically melt, if the crappy internals inside the alternator don't fall apart first.
If you've got a 2G, Motorcraft later made the 3G which is only slightly larger and has exceptional performance (160 amps, I believe, and 80 at idle alone) and reliability. Slight modifications to the bracket may be necessary to make room for the larger body diameter. Mounting holes are the same.