I was planning something similar a couple of years ago. The thread I started is
here, and some of the thinking may be of use.
In the map linked by
@deptfordmarmoset, the orange route looks like a sensible starting point, but it'll give you some stiff climbing after Pocklington. Instead of heading towards Driffield you could take a more northerly arc, picking up a very nice valley road (which I rode in 2017) at Helpersthorpe and taking you almost to the finish.
If you keep to the east of the A614 after Boothferry Bridge, you'll get a much gentler crossing of the Wolds, and there are plenty of minor roads to choose from. There aren't many places to crossing the canal though, so you have to plan around that.
I don't know the area at all, but there seem to be some nice roads across the flatlands east of Doncaster which might be useful.