Whoa!!!! The springs at 110# on the seat and with an actual realized lift probably under .400", You'd be lucky to see 240# over the nose, springs are the least of Your worries.
You can't put those heads on a 273 w/o a major bore notch/relief, the valves are going to be close to hitting the deck, even with that low a lift value....You'd better check that out before anything else!!