[Adrian472]

Eric
Firstly i would have to say it all depends on what kits you are looking at buying and what suspension layouts they offer.
3 and 4 link rears are typically for a solid axle and IRS is a independant setup with top and bottom links and a halfshaft per side.
If your plans are just a sunny day cruise then either a 3 or 4 link rear would be fine and wouldnt justifiy the added cost of a IRS set up.
I hope this infomation is some use to you.

Adrian