IRFI540N install orientation and lack of availability

[NE5U]

Q6 and Q7 are somewhat unobtanium. I found some allegedly NOS for sale on eBay but that's always a crap shoot. That said, the crooked logo on the supplied transistors makes them suspect as well. The scarcity of these parts does not bode well for future repairs. Is there a substitute?

The silkscreen shows the tab is away from the edge the board yet the rear panel has what appears to be a place to heat sink the MOSFETS. Which way are they supposed to be installed?

[NE5U]

I found all of the documents so I can answer the orientation question. As you would expect, the MOSFET is attached to the back panel.