65 Barracuda... Got BAD News...

New valve covers are cheap. Valve seals are almost as cheap but take about 2 hours to put on and a special tool, along with a pretty good mechanical aptitude. A 318 short block is cheap too and will bolt in with all your 273 gear. YOu can even use your original crank if the convertor snout on the 318 is the newer size. The balance on a 273 is the same as a 318, neutral as the pistons weigh the same and use the same rod. I did a 318 short block on my spun bearing 273 4bbl and put in a Herbert stage 2 cam in there and the 318 was faster by a country mile and still idled like a stocker. 340/360's are big and powerful but exhaust is a challenge as you dont want to use the original 273 logs on the larger motors, youll cheat yourself a few HP. Do the gaskets first, then a seafoam treatment or the cheaper "dribble a water hose in the carb at a high idle and watch the crap fly out the tailpipe" method.