Ford GT cams should gain a gt500 about 50hp. They aren't a very aggressive sounding cam. Im not sure weather they would work on a marauder. I would imagine so since they're a Ford 4v modular cam, however I cant make that guarantee.
Cdd408, that's great man. If you wanna buy those, go ahead. These cams arent damaged in any way and dont appear warn. I was trying to be an honest person by including milage. I also believe that I'm asking a fair price.
As far as the L&M cams, the pistons that were setup to run these came with notches. I would imagine with the high lift, yes.
I have a video of the FGT cams running somewhere. I'm not sure about the L&M ones.
L&M Cams
It all depends on how its done. I have personally pulled the head off one of these cars leaving the motor in the bay. It took me 4 to 6 hours, but I was looking for other issues along the way.
Im not sure what a shop would charge. They may prefer to pull the motor as its much easier to work on outside the car.
I had a friend who planned on doing their cam swap to a different nsr cam without removing the head. They were going to pull the valve cover, use a chain wedge to hold the chain in place while they swapped everything. I'm not sure how he ever made out with it.
The cams are no springs required. In essence you would open the motor, remove the old cams, install the GT cams. Set timing / degree. Close motor and tune.
Edit: Yes, it should net you around 25 - 50 hp with tuning. It is a larger cam than our stock cams.