R5 P7 what fits what ???

Hi guys
New to this site so
Im in Aust and i race a historic touring car Valiant Charger (for your info see my web site www.racingcharger.com) and maybe check the link to the series to see what we race against (comaro's mustangs ect ect ) any way i have a R5 P7 engine in the car and have now been told it has to be replaced with a R3 at the end of the year (im really not Happy !!!) but thats the end result
The problem is they dont like the heads (valve angle) so does anybody know does a indy or any other head bolt on ?? because if so that will save me a bundall as i have 2 new blocks and 2complete engines that i have been running

Do you want the heads to fit the r3 block? or the r5? You were not really clear.