sd.kfz.234/4 7.5 mm L/48 Service Questions

If you mean Dragon kit 6814, then I believe it is common wisdom that this is a "paper panzer".  It is based on the 324/3 with the normal L/24 gun replaced with an L/48, presumably the KwK 40.  I imagine the mounting would have struggled with the recoil force of the more powerful gun, especially without a muzzle brake: the PaK 40 mounting in the 234/4 for essentially the same gun was more substantial.  BTW, there was no L/46 7.5cm gun: L/43 or L/48.

Only 88 of the 234/3 were built anyway, followed by 89 of the 234/4.  The role of the 234/3 was essentialy fire support, although the shaped-charge round for the L/24 was reasonably effective against AFV's (better than the 5cm AP in the 234/2).  That changed to a principally anti-tank role with the 234/4, which was essentially a wheeled panzerjager.  

So I can see the attraction of substituting the L/48 gun to quickly re-work 234/3 into a virtual 234/4.  If this could be done on the 234/3 then it could also theoretically be done on the 250/8 and 251/9.  But as I said, I don't believe it ever happened: possibly a one-off experiment, but no more.

The 234/4 was in production only for the last five or so months of the war in Europe. At that point, especially after the massive losses of armor on both fronts, the vehicles were likely thrown into ad hoc kampfgruppen as they came out of final assembly. A quick image search of "sdkfz 234/4" will show a few in various late war settings and conditions. 

Thank you so much for the reply. You were right, it is kit 6814. I thought it was odd that it was designated 234/4 when it more resembles the 234/3. The "paper panzer" fact would explain why I could not find any historical data. Thanks again for the insightful response!