Not sure if you'd need to on a Mk.1/2 Escy - the only reason I took the balancers out and nailed on the Sierra sump onto mine was because I didn't have time to bugger about with the engine going in and out while I modded the 2.3 sump to clear the Sierra steering rack and crossmember.

And, now I know about it, the starter thing with the 2.3 sump / Sierra MT75 box would have been a bitch to find out about at the last minute too.

If Finpower is retaining the type B / N / 9 box he should be able to find a bellhousing with the starter aperture on the correct side so swapping the sump wouldn't be strictly necessary unless the crossmember clearance became an issue.