I have a Winchester top level spec sheet for their 38 Spl +P 158 gr LSWCHP gotten from another sight. I'm going attempt to contact Remington for their version.

I knew Remington employees growing up in Connecticut- they had a plant in Bridgeport, CT. They are all gone now. Would had been great to had the opportunity to speak to them regarding their work.

Anyone out their have factory Ammo specs?

You're not real clear about what "specs" you're asking about. Remington ammo velocity/engergy tables are available on the Remington website.

I doubt you'll see much difference between Federal, Remington & Winchester. They may use slightly different primers, powders* and bullets, but they're up against the same pressure limits. Any difference might well be due to different test rigs.

*Since Hogdon appears to control both IMR & WW powders, exactly what powders anyone may be using is unknown. Back in the day one could assume that Winchester was using Olin powders & Remington Dupont since the conglomerate who owned the powder companies owned the ammo/firearm company.

The drawing depicting cartridge outline and dimensions along with ballistic measurements.