If replacing an isolator (diode based) you need to put alternator to battery back as stock. So your alternator will go to your starting battery. The new Bluesea 7622 ACR will go between your starting battery and house battery. As said, the wire that is currently from the isolator to the house is most likely not large enough to handle the possible current capabilities of the 7622, so you should replace. I use bluesea MRBF terminal fusees at the starting battery and on the ACR side of that cable.
Here is a picture of a MRBF fuse on the starting battery.
I also use a MRBF fuse on the "B" terminal of the ACR which goes to the starting battery. The ACR is on the right. Where ever your current isolator cable connects to your house side would be where you connect the "A" terminal. You can switch the two terminals if it wires up easier. The two larger cables, one comes from the Inverter and it has a Class T fuse on the inverter side, the other was is from the house battery which has a Class T fuse
This picture may be more confusing as I have some other Bluesea switches for a battery disconnect and solar disconnect.
If you have a original SMB you most likely don't have a Fuse close to your Hosue Battery, but that would be a good thing to do also.This is what I did for that.
Class T fuse protecting the house battery.
Polycase ML-47F*1508 7.63 x 4.63 x 3.09 in. NEMA 4X/ IP66 rated for outdoor use
Polycase ML-47K 0.06 x 7.12 x 4.13 in. Mounting Panel
Polycase CG-17 Cable Gland
Blue Sea 5502 -Class T Fuse Block with Insulating Cover - 225 to 400A
Blue Sea 5118 -Class T fuse 250 amp