What cam should I get?

The retainers are not what determines the max lift ona stock head 273, 318,or 340. The height of the stock guide does. 360s need new retainers, or replacement of the exh rotators if equipped. I just put 8 used stock retainers on my '87 360 replacing the rotators when I swapped the springs and cam with XE262 and IIRC 901 springs. To get your comression ratio as built, you must pull off a cylinder head too. Then you have someone cc a head chamber, and measure where the piston is in relation to the deck surface of the block and grab the part number for the piston. Then you can figure the true compression of what you have. It also lets you see what you have for valve releifs and if you need to worry about piston to valve clearance.