Front Cab Support, use OE or Slip On?

[lintcollector]

I have some body work to try and figure out, and LMC Truck said to talk to guys who know about fixing old trucks, so I'm ready to ask the masters...

I have a bit of a rust problem and need to know if I'd do better getting the OE part (LMC 38-7950), or to get the Slip-On (LMC 38-7951) for the front cab support. I don't know enough on which way to go, any help / recommendation would be appreciated.

Below pic is what the front cab looks like from below on both sides.
Here's the reference to the LMC page/catalog: Page 13

Thank you in advance for your assistance.

lintcollector