How a tractor performs has a lot more to do with the gearing than it does hp under the hood. If hp is not used sensibly it will tear things up.
chieffan is right you can get a lot done with a stock TRA-10D on a 1050 its all in using the gearing properly, there is plenty of power for all the attachments and towing things.
Thanks WrenchinOnIt for posting that link from Husky, I was just visiting Husky on Saturday and had a chance to see his Briggs twin conversion on the H14. Beautiful work, it looks factory, nice detailing, but according to Husky it took months and months to do the conversion and restore.
If you are doing it on the 1050 I don't no how much more benefit you will get out of it because it is a gear driven machine the gearing is what gives you the torque and power. Husky did it on a hydro unit which has the ability to use the increased HP more efficiently. I know my H14 was upgraded to a XL OH160 Tec engine in the late 1980's and it will use every bit of HP that that 16HP engine will put out because of the foot pedal control. You can go from zero to full power by just pushing the pedal all the way forward in a matter of a second, it will dig a hole with the rear tires before it will bog down. From what I have read on the specs if it was reliable info those Eaton 10's can handle up to 50 HP, they are very rugged hydro units.
Maybe Husky will chime in or someone else who has done a similar conversion.
Again good luck with your project.