If using aftermarket pistons there should be no problem but of course this needs to be checked... The factory LS7 cam was .600 lift but of course this was with the 188/990 heads so the ovals may be somewhat different in valve clearance...?
The lower lift cam would work no problem for sure and no need to machine the guides too... With the larger lift cam the guides will need work (.125 off should be fine) But also depending on the pistons valve clearance needs to be checked on anything over .550 lift... The 781`s that I`m running were fine even with .604 lift on the intake side but was using 1.8 ratio rockers and have aftermarket pistons... I swapped back to 1.7`s and saw less valve train noise and for sure less abuse...