Well, on an 8" I wouldn't go larger than 275 in either 60 or 50 series tires (275/50 is really pushing it, but I've done it) The 275/60 is a 28" tire, 275/50 is slightly over 25" (not actually doing the math here) so its pretty short. MOunting the bare rims on the car is a could idea to get a visual about clearance to springs and fender. You can even make a cardboard crosssection of the various sizes you might consider (its easy)

For the fronts a 235/60 or 245/60 is good, but I am not sure the 245 will fit--others will know. FOr the fronts the issue is clearance to the frame segments and the fender itself. The 8 inch rim will be more than enough to handle the size.