I don't see any issue with mounting an 18" wide tire on an 10" wheel. I run the 39.5x15.5 and a buddy runs 42x15.5 TSL's on 8" wide rims with no issues for several years...so if you can run 15.5 on 8 you can run 18 on 10.
In pictures those 42" Boggers look really skinny and the 42" TSL look wide, would think it might look a little weird if that is true if you put TSL front and Bogger rear (of course I'm talking looks so it might not do as well at a car show
). The slight difference in tire height should not be an issue.