I have had a similar round in a contender for nearly 30 years...called the 358 Bullberry..jus the 375 win necked down to 358 or the 30-30 necked up. Has a short neck and about the same performance as the 35 Rem in a 14 in contender. I had a 357 mag Handi rifle barrel that would not shoot and I had OTT rechamber it to 358 BB and it is one of the most accurate guns I own.

I have not heard of the 350 Maine Guide so I do not know the exact dimensions but it certainly would be similar and very doable in a contender...

shortgun