Haven't seen the SPC piece before, but here it is, the SPC upper control arm. It mentions all steel contruction. Doesn't say but looks like standard bushings, NOT A HEIM JOINT, Peter would know. Price retail on the SPC adjustable piece is $482 a pair. The previous posted upper control arms were $270, that is a difference of $212. Just saying this because the topic of this post is Tubular control arms, too much. Here is a exerpt from the SPC ad.

Product Description
B & E Body, Passenger Side, Front Upper, Fully Adjustable Style, Steel, Black, Dodge, Plymouth, Each

These SPC Performance street rod and musclecar control arms are available in fully adjustable upper or tubular upper and lower control arm configurations. These arms allow you to fine-tune your suspension to meet your exact needs. Tubular-style arms are available to accept stock, coil-over, and air ride suspensions. Camber, caster, offset, and arm lengths are quickly and easily changed on all adjustable arms.