Does the cars suspension need to be under load when their welded in?
How much should I expect to pay to have them installed?(just so i dont get ripped off )
At a mustang shop around here it's $300 to buy their subframes and have them installed or if you bring your own (I bought some full-length powdercoated MMs) the install was around $150.
Most good shops will install them on a muffler shop style life (raising the car from its tires). It IS important to have the car loaded on its suspension.
Install prices, I'd expect anywhere from $70 if you get a deal from a friend to prolly about $150 otherwise.
It depends on how they install them. The place I went to completely grinded down the surfaces to get a good weld and then painted the area after the welding to prevent rust. I forget how much it cost but it was almost a three hour job.
When I had mine installed they tack welded them in place crawling under the car and then lifted it by the frame to finish everything off. It's a well known Mustang shop in Houston so I figure they know what they are doing. I was charged $120 and it took the guy almost 2 hours.