G'day tombutt, on outers a bloke fitted the later model type gv steel front diff and carrier to his grand vitara (about a 98-99 model) and he didn't have to do any mods to his sump according his build thread
http://www.outerlimits4x4.com/ftopic144 ... 74ac2b0279
so with you having a V6 and a different sump ... you might be lucky
The problem I had with my J20A SWB Vitara is the part I have coloured here red what was hitting the sump.
The guys at ARB Port Macquarie called once they noticed the problem and after having a look myself, the fix we decided was to modify the sump and push part of it back about 25 mm in with an oil press and in the end it looked quiet good
until the sump was put back on and it leak around where a gasket would go 
(no gasket used on J20A Vit Sump just some sort of goo sh!t). I have uploaded a picture for you that shows the modified sump.
Using sockets between the block and the sump, around the bolts, the guys slowly squeezed the sump back to square and using a straight edge checking where the sump needed to bend, apparently it is bit of a ralley car trick - not really sure what that means
This fixed the leaking sump issue 
Another option was to modify the bracket or make a custom one but I had to make a decision whilst the car was on the hoist quickly and modify the sump at first looked to be the easiest and best.
A diff drop I am guessing would of been another option to give you the extra clearance so good idea.
Here is a picture Steuy has on his build thread of someone elses car I think that shows where the member had to be modified.
