I think you are talking about a tractor? You can usually modestly boost your power without killing the drivetrain depending on how you use it, shock loads, etc.(see my comments in thread50-171764) What brand/model?
I don't think you will be able to stroke the engine without a custom crank. According to my research this past hour your engine is as big as the family gets. (I think the TL70-100 uses the Cummins/Iveco motor.) And even if you bump the displacement by 10% you only get 83hp with proper fueling. Not worth the money/effort.
8045.01 - 95mm x 110mm
8045.02 - 100mm x 110mm
8045.04 - 103mm x 110mm
8045.05 - 104mm x 115mm
8045.06 - 100mm x 115mm
8045.25 turbo - 104mm x 115mm
Current Iveco 8045E, 8045SE, 8045SRE – 104 x 115
The easiest way to boost HP is to turn up the fuel pump. With your non-turbo engine this will give you some black smoke and void your warranty, but you obviously don't care about that. You might check with some tractor pulling type forums for tips on this. (1970's all over again.)
I also see that there is a 8045 turbo engine. Provided you could find the parts to convert your engine reasonable this would give you the most bang for the buck with better fuel efficiency. Ideally buy a junk tractor/motor for the bolt-ons.
If you wanted to get crazy there is a 5 and 6 cylinder version of this engine also. Just stretch the hood.....
ISZ