you can advance timing... quite a bit actually but be aware of detonation... those kill !!
... so since you got new rod/rings... dont kill it now .... i suggest around 10-12BTDC... not more... at 15.. it will detonate even with 92oct fuel..btween 5500rpm and up. (10-12 with 92 oct fuel is safe) anyway if you hear something at high rpm... just pull over and bring it back a bit....
next mod... turn the cap of the air filter upside down (if your a 350 fan you sure know this one !!
get yourself a K&N filter for this engine (wich im sure is available)
good set of wire/plug...
If you have AC... get that belt off....
now your good for that super 70hp we almost all have !!
Have fun !