Pak 40/Marder III H question

Modeling Subjects Armor
1

Confessing my ignorance here but…

I’m thinking of scratch/bash building a Marder III ausf. H based on the hull of an old Italeri Pz. 38(t) I have lying around, and I can get the Tamiya towed 75mm Pak 40 on the cheap and use the barrel for my Marder project, but I was wondering…would that barrel be accurate? They’re the exact same gun, right?

2

They did indeed use the same gun.

3

I thot it was a russian gun 76.2 cm/mm or something?

4

The Russian 76 was used on the earliest version of the Sd. kfz 139.