The smart mode converter/charger needs to be able to produce 17-20AMPS DC Current per 12VDC battery in your bank if you wish to ever re-charge your batteries to their 90% charge state in a quick three hour charge time... I have three 12VDC batteries in my battery bank and they demand around 53AMPS DC current when first hit with 14.4VDC from the converter/charger unit.
Your 87 model RV will most likely not have a smart mode converter/charger unit which would be a great addition for upgrading things. The smart mode units really take great care of your batteries automatically. Might want to take this into consideration as well while you are upgrading things.
Camping season for most of us is just around the corner here - We are looking forward this season to do some upgrading things ourselves... I'm looking for changing to four each TROJAN T-1275P 150AH 12VDC Batteries and maybe some solar panels. My current battery bank is using three each 85AH 12VDC Standard issue Interstate batteries (255AHs total). Have done good by them since late 2008 with my OFF-ROAD POPUP camper... I need more power now...
Roy Ken