This is what I use in mine. Description from their site
Redline 80W250 GL-5 GEAR OIL
Recommended for SAE 250 or where SAE 140 does not provide adequate protection
Alternative to Red Line Heavy ShockProof® in problem Nitro Drag Race Vehicles
Can be used in Model A, Model T vehicles and Antique/Classic cars calling for 600W
Reduces noise levels in Morgan 3 Wheeler bevel boxes
Excellent for off road use where SAE 250 is required
