Any sparktricians in the house?

We're looking at replacing our 20 YO Whilrpool oven microwave combo with a Thermator but now I'm nervous about the power requirements. The new oven is rated at 10200W (42.5A at 240V). Our current oven circuit has a 40A breaker and 6 gauge aluminum wiring but the installers cut the jacket at the top of the box so I can't see what temperature its rated for. Can I replace the breaker with a 45A? Would that even be big enough? I think replacing the current wiring would be a huge PITA without cutting holes all over the ceiling.

I'm going to try calling a local electrician tomorrow but everyone is remodeling right now so I'm not sure if I can even find anyone to take a look at it.

Thanks in advance!

Being conservative, #6 aluminum won't do it.  It is rated only to 40 amps.

OK. That's what I thought. Thanks for your help.

You would need number 6 copper or number 4 aluminum.  

Called an electrician and he came out today. He's going to run a new 6/3 copper cable and install a 50A breaker.