American armor

I did not know they apparently made a cast-hull Lee!

In June of 1941, the Ordnance Committee began a program to seek out different hull assembly methods. The first of them was casting. The upper part of the hull was cast as a single component. The side hatches became smaller. In addition to simplifying production, the cast hull allowed for more rational use of the fighting compartment volume, but increased the tank's mass to 28.6 tons.
Unlike "regular" M3s, tanks with cast hulls were not exported. All of them were used by the American army.
The second alternative to a cast hull was welding. Welded hulls were more promising than cast ones. The shape of the hull remained unchanged compared to the M3, but there was no need to drill holes in the plates for rivets. The welded connection was also stronger. Finally, the cast hull had its own drawbacks. The cast armour was weaker than the equivalent thickness of rolled steel. It's not surprising that welding became the main method of assembly for American tanks.
http://tankarchives.blogspot.com/2017/10/medium-tank-m3.html