I have no idea (or interest!) in whats available, just saying what kind of size you need to fit the ops preferred width (265) on. After that it's upto to the OP to find out or others to say whats actually available, you would have to get the nearest equivalent. there is some degree of flexibilty in terms of what tyres will fit what rims. I'm currently running 235s on 8 inch rims, but they were apparently a bitch to fit! But that was what I happened to have left over in my garage and at £600 a set I wasn't about to buy a new set! Also I went for an 8inch rim, so I could get a -33 offset (not possible on 7inch rims) and not lose too much on the steering lock, knowing there was room in the wheelarches (just!). You can get any wheel you like made (assuming it's physically possible), at a cost. 19.5x6.5, 7.5, 8, 8.25 or 10, whatever you like!

My main points are:
a. I don't think this will work without a great deal of modification
b. It will have undesirable consequences you don't appear to have considered. If as tacrman has suggested, you aren't just running out of revs you may end up with an even lower top speed because the engine won't pull the gearing!
Then there is the acceleration I have already mentioned, you may find hill climbing a chore. then there is physically fitting the wheels, you need to consider steering lock, fouling on bodywork and suspension components etc and in with that as well as the size of the wheels you need to think about the offset, which you haven't mentioned. you may need a big -ve offset for the tyres you want to clear components on lock, which may require a custom wheel. After all that you need to think about the additional strain all this will put on other components such as steering, bearings, transmission etc. You may need a suspension lift, which will have an impact on steering geometry so steering may require modification. You may find you need to extend propshafts, anti-rollbars don't fit etc etc. Of course, all this can be overcome, but there are a multitude of things to consider before undertaking such a mod. I'm not saying it can't be done, just that it's not as simple as just chucking on a bigger set of wheels and tyres.

Your opening up a can of worms making such a big mod I reckon without some serious investigation first.

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1990 Landcruiser H60. Full rebuild completed 2014