[LS short box]

Yeah you have do it with relays. The wiring in the trans shaft module can't handle the amps of the starter wire. I would do it. If you or someone else starts the truck in drive or reverse it could be bad.
Side note. I've used Lokar shifters on a number of LS/4L60E swaps and they have been bullet proof. But they have gone crazy price wise. Even the cheaper B&M shifters are close behind price wise.