I was going to say if you are tight for room then you could go to an electric fan and mount it on the front of the radiator. That would probably give you about an extra 4 inches of clearance. But after looking at many of the modified trucks you should be able to put it in with no big mod's to0 the firewall. I wouldn't attach a mount to the MII cross member. A couple of options there, frame rail engine mounts are available at most HR shops or build your own. If you keep the motor mount pin level with the top of the frame rail should give you a good height for the motor. This will probably give about 2-3 inches clearance from the bottom of your engine to the cross member.
