Got a boxed model a frame and a spring behind drop axle setup. im using a perch kit that welds to 3 inch tube style crossmembers but i still have my stock front crossmember in place at the.moment. Should i put in a tube in front of the stock member or remove the stock one and fabricate some radiator mounts for it?
That depends on what wheel base you wish to end up with. With a spring behind, you may need to remove the frame horns ahead of the new cross member.
Crossmember forward of stock placement + suicide mount + spring behind = crazy long front end. I would weld a temporary piece of tubing across the top of the rails, remove the stock crossmember and mock everything up so you don't end up with something that looks ridiculous.