Oginme, I know Glacier Tanks makes Electric tanks up to 10bbl.
John, I can't imagine you would know your boil off rate on a new system, as it will differ greatly from your current system unless you're not changing boil kettles?
what is the design of the "Mash Tun" as with a system that large you may need a separate lauter tun depending on mash tun design (usually systems that small are pretty straight forward though I would still recommend installing some form of DP measurement for lautering)
as Oginme stated, setting up a 5g cooler mash tun system is practically the same as setting up a 3bbl system. Best practice is to physically measure any and all losses, record step change times, etc. With no other knowledge of the system you have, system you had, and what wasn't "dialed in" it would be impossible to troubleshoot any issues.