I'm not sure what cfm the windstar fans pull, so can't really help with your decision on using them.
As stated above, keep the relays close to the fans. You really want to mount them so that the wiring run between the battery, relay, fan is as short as possible. I'm not saying string them up so you can play banjo on the wires, but don't route the wire around the backside of your firewall and keep a 5ft long loop in case you want to move it later. They're fans, simple, ignorant, electric motors, nothing fancy. Good battery connection, 12ga wire, GOOD GROUND path, you're golden.
Make sure your battery to frame / frame to engine grounds are good.
My car is a complete hack, so keep that in mind. I have my battery in the trunk, main battery cable going to fuse box under the dash. I used 2 12 ga FACTORY 1964 wires going through the FACTORY fuse block/firewall harness to feed my relays for my fans. As you saw in the other thread I have my fans wired up with 3 relays the same way 98-02 Z28s are wired up. Fans come on low (series) when getting warm, when fans go high they go parallel. I love this setup, the fans rarely ever kick on high and you can't hear them running on low.
As many friends as I have come over and ask for wiring help I usually keep relays around the garage. These aren't the best, but they work, and what I normally use:
Not too proud of how the wiring looks, but here's my setup. Both of the power wires come in to the horn relay, used that as a junction block. Power feeds the 3 cheap, amazon/chinese relays, then 12 ga wires go out to the fans. I mounted the relays close together on a piece of 1x1/4" aluminum and bolted it to the radiator. You can use blue crimp female spades (get insulated!!) or get relay harnesses. I used the harnesses that came with the relays. They're "gold" coated so shouldn't corrode over time. Time will tell though. These fans flow so much air the first time I cut them on high they sucked so much junk out of the radiator fins I had to step away from the engine bay and clear my eyes.