Leg, Lugs, and Support Rings:
Pressure Vessel Design Manual by Dennis Moss
Pressure Vessel Design Handbook by Henry H. Bednar, 2nd Edition
AISC straight-line method
Lifting Lug:
Line Load Method from Pressure Vessel Design Handbook by Henry H. Bednar, 2nd Edition
Saddle:
"Stress in Large Horizontal Cylindrical Pressure Vessels on Two Saddle Supports" by L.P. Zick
...