Welcome to CHR! I would say it's definitely worth changing the heads if you go with a set offered by a quality aftermarket supplier. You'll get improved flow, plus they'll dissipate heat quicker allowing you to run a bit more timing without fear of detonation. You can get an adjustable pushrod from Summit or JEGS to determine needed length, if the head supplier doesn't provide the info - https://www.summitracing.com/search/...rder=Ascending

Some of the other guys have recent BBC experience (Glenn Sexton?, Ryan/40FordDeluxe?) and can probably point you toward some specific heads.