not hard at all, i used the stock rubber mounts to hold the bottom of the radiator in place and had some hooks bent up to hold the top inplace.(almost like what the fox body stangs use)
to hold the fan to it you do a little trimming to the shroud and then i used some things from summit to hold electric fans to the radiator. you could probably get away with zip ties for a while tho
I dont recommend the pull-through zip ties for the E-fan - too many people have had them tear out.
The radiator comes with a lip with holes at the top and bottom - you can work with that instead.
See Jason (Onelive95 on the Corral - I cant remember his username here. He just parted out his car recently if that rings a bell) - he did a universal radiator with little pieces of pipe welded to the bottom so it slid right into the OEM footings - slick!