I don't think either would be difficult. Impco vaporizer or similar, the carb and and associated plumbing would likely do it. You could easily use a 30lb or even a 40lb tank, 30lb is common, just install an LP tank cradle like on a forklift to secure it. I would like a 40lb, but full its going to be heavy to lift over the loader arms, so I have one spare 30lb, could use one more actually. The tin will support it and if yours is modified already, why not. Mine just has the hood removed, but this tractor has seen a zillion hours and the tin is not very good on it anyway. The 30lb tanks are not that hard to deal with, get a few, you'll get 4-5 hours run time depending on throttle, and they change quick. Winter time can be trouble if there is a problem with the vaporizer, I cover the engine compartment with a furniture blanket, use that heat to keep the tank warm and I keep the tank I need to use in the heated garage. The oil stays very clean, with the hours I put on it annually, I can extend the oil change interval much more than gasoline, and it seems engine wear correlates to this, they don't wear out nearly as fast. LP I think is less HP, compared to gas, but mine does everything I have needed for in the last 12 years, only using the rotary mower do I notice it bogging down a little in tall/thick grasses, but tolerable, just working harder than other tasks.
On the other side, thats a nice clean model, you could go the other route, source a fuel tank, heat shield, carb, plumbing etc, and tinwork as needed, no tank up top, though mine does not obstruct the view.
Mine as is with LP, just a workhorse anyway, if you were a collector, I suppose making it a factory correct LP may be a consideration, but for work and chores, etc. either way you can't go wrong. LP is nice inside a building, the tanks change out with ease, I've gotten used to mine, and the fuel was cheaper way back when 12 years ago, not anymore, went the other direction, that is for sure.