what heads to run on a 273

Yep, 70 Duster is correct. 302 casting heads are a good choice for the small bore 273. They have a bit larger ports that flow good and have a heart shaped combustion chamber that is relatively the same size as the stock 273 heads so you won't loose compression. They also have hardened seats so they're unleaded gas friendly. Mopar used them in the mid to late 80's 318's found in Diplomats and Le Barons (M Bodies) (from Mopar Muscle article)

Chrysler's small-block cylinder head design changed very little until 1987 when the 302 casting (last three digits of the casting number), commonly known as the swirl port, was introduced. While the 302 casting, as well as the later 308 casting, were most commonly found on low-performance 318s, they shouldn't be overlooked for a performance build. Even with small 1.75-inch intake and 1.50-inch exhaust valves, the design of this head's heart-shaped quench-style combustion chamber makes it a good choice for mild to moderate performance. An engine with these heads in stock form will outperform an engine with stock X or J castings simply due to the improved combustion chamber design. Additionally, these heads have hardened valve seats, which make them compatible with unleaded fuel. The swirl port heads were utilized through 1991 (302 casting) and 1992 (308 casting) and respond well to port and bowl work, offering better power potential than all of the earlier small-block heads. Another nice feature of these heads is they utilize valvetrain and intake manifolds common to early small-blocks, so parts are readily available. Simply bolt these heads to your small-block and enjoy the extra power they provide.

Magnum Heads



Read more: http://www.moparmusclemagazine.com/...opar_cylinder_head/viewall.html#ixzz1l8b5PH2l