Please report back with your review here when the replacement is done.
Yes, the MK4CBC will fit the factory routing of the MK1 pickup.
I had the stock MK1's on my SRF705 replaced with a pair of MK5CBC years ago. The sound became too thick. Not the kind of fretless sound I had expected. Fortunately, I had them wired through a push-pull potentio, which functioned as the default dual coil and optional single coil selector. The outer singles sounded much better, but then I got the issue of single coil noise when the pair volume knobs were not set at an equal level.
I'd had this configuration for about 3 or 4 years before I reverted the pickups back to the MK1's last year. To my ears, the stock MK1 pickups sound much better for the kind of midrangy fretless tone I'm after.