A tape measure is good enough to tell the difference in bore sizes. A 4.2 will be just shy of 4 1/4", and 4.4 will be a little shy of 4 1/2". Please report back if you find it to be 4.4", and I will advise on a head gasket.
Run the suspect piston down half way into the bore and then rock the front pulley back and forth while you watch the piston. There should be no visible hesitation of the piston moving as you rock the crank back and forth. Compare with the other pistons if need be.
If there is a problem, you will need to remove the oil pan. This will require it to be unbolted from the front bolster. You can remove it entirely, or roll it forward a few inches on longer bolts. The choice is yours. No need to split the engine from the trans.
A loader very much complicates things for sure. Depending on the brand, it will likely need to be removed first.