good heads to get me by?

For the 273, use either the 302 heads ported, or milled down 1.88 360 heads, except measure what you had for chamber volume and then go another 2-4cc's smaller with the 360 heads...and of corse have a perf valve job on them..they should flow 215cfm or so.

the 302/675/920/178/315 heads will all flow the same give or take a few cfm, even ported, the open chamber versions may even flow a lil more.
Stock valve 318/273 heads flow 165'ish int/120exh cfm and when I port'em they go around 205/145 *with stock valves*fwiw