I just installed a non- stock 1 piece carpet in my ‘54.
Go with slits , it makes the job reasonable, and you will be the only person who knows or cares that the carpet has been cut.
Measure twice. Then use masking tape to mark the location of a pedal slit. Then be bend the carpet to enable you to check the tape location for accuracy. Make the cuts individually. Verify each before going on to the next.
A carpet guy could do all of this in one easy operation. I am not a carpet guy. I incorporated all the safeguards I could think of. The results weren’t perfect, but the were satisfactory.
