My thought was he get a later yr 318 and build it. No sense building a 273 these days unless you have a real commando 4 brl car or something. No one will know cause it looks the same.
I guess, from my experience, new is worse. The 273 had all the good parts. Forged crank and rods, floating pistons, solid cam, better heads, we always built them, no special parts, just upgrade the cam add a windage tray and away you'd go. If you got hold of 68-69 pistons you had a zero deck short block. 340's were the same, only quicker. 318's needed special pistons, and only had low performance internals. 318 2 barrel engines did not make 230 horsepower, and were not worth racing. Like everything, if you throw enough money at them you can make anything run. I am not a drag racer like you, but all my friends raced or still race. A second or two in the quarter mile does not bother me. I want it all. Quickness, reliable to cruise all day at 100 mph, top end of at least 140 mph and get good gas mileage down around 70 mph. My brother and I put 500,000 miles on high performance 273 Barracudas from east to west and north to south. I love how a 273 zips up to 6,000 rpm effortlessly with a 4 speed and the sound of the old 2 1/2" straight through single exhaust running all out.