as far as SAR goes, you probably wont be doing much with your truck other than going to and from searches. i have only once use my rig in a 4wd capability on a search. it is very rare that you will be "mounted" for searching. and when you are you will not need all of that(lockers, huge tires, dual cases, SAS ect) i cant think of a situation where that would be needed. there are helicopters and other resources available, and coordinators would try their best not use volunteers private vehicles for actual mission tools.
if you have further questions as far as how to set up your rig and what gear to get, ask the guys in your team/group what they have and recommend. i see people joining all the time and going out and dropping $1-2k in a couple of weeks on gear they dont know how to use or will never use or end up not liking, either way it was/is a total waste. talk your group and find out what they like and dont like and get their recommendations on what to get ect. also feel free to contact me and ask me about gear. but i think your truck should be your last priority in this aspect. -build it to be super reliable and dependable number 1 so that it wont break down on you and leave you to become the one needing rescuing, and just use some common sense when out on the trails with it, dont over drive it or yourself.