Nuru,
Here is the loader pic and dimensions that I promised, if the pic hasn't been attached I'll try again.
The dolly is made of 2x6 (5 1/2 x 1 1/2), the outside dimensions are 5 feet long by 30 inches wide bolted together with 3/8 carriage bolts. (2) 5' stringers, (3) 30" cross members and (2) 4' long temp load supports.
The bucket end cross member is on top at the end of the stringers with a second cross member also on top spaced about 4 inches from the first. A piece of flat steel between them protects the stringer from the bucket edge. This space captures the bucket to keep it from sliding fore or aft.
The third cross member is bolted to the bottom of the stringers to clear the tractors front PTO bearing.
Swivel casters are bolted to each corner.
Two 4 foot long 2x6 are ripped for about 1/4 inch clearance from the ground to the bottom of the stringer. In the pic one of these is in place and one is free in the foreground.
This set up fits under the tractor, rolls easily on clean concrete floors and has no tendency to slip off when I push sideways on it.
The bucket dump angle and parking stand angle keep most of the loader weight off of the hydraulic cylinders and allow one hand connect/disconnect of the hose connectors.
If you use less dump angle you will need to increase the dolly length.
Keep the loader control valve out of regen position so the bucket doesn't flop if you go over center.
Slide the temporary load supports under each stringer as shown and they will support raising the tractor front wheels off the ground to unlock the loader and the parking stand feet which will first land mid dolly. After the parking stand feet have slid close to the casters the blocks can be slid out and saved.
Lot of words for a simple dolly.
Good luck