Not really.
If you're going to use 6LQ's in that thing, best to keep it at 450-500 watts PEP output, and about 75 watts AM carrier.
With 6MJs in it, it has about 30 percent more Pdiss than the 6LQ's... Also, if it came with the "RF Black Cap Double Strap Plate" connection tubes in it, you can increase efficiency by modifying the output network a bit... The difference in 6LQs and 6MJs is Cout and Pdiss... And it's NOT trivial... IE, the black cap tubes WON'T work in a D & A amp, or many others that used 6LQs without some tuning work on the output side (changing the coil turns / spacing).
If you get the option, GO WITH THE BLACK CAP TUBES, and run your amp as it says in the manual. The black cap tubes have 2 plate connections internally, increasing the cooling a WHOLE HEAPIN HELPIN (like, more than double!!!), so they last LONG time. They also have a 40 some watt Pdiss because of that, whereas the regular 6MJs had a 35 or 38, and the 6LQs where at 28-33, depending on mfg and cooling design. These numbers are going from memory, so I could be off a watt or two, but you see the reasoning for lower output figures when going to the 6LQ tubes now. They REALLY aren't the same tube, just the same pinout.
--Toll_Free