I sure wish you and everyone else would put your location in under your name so I (and the rest) can curve the answer best suited to your octane limitation.
I see the 2 point octane difference as at least .5 less on the ratio and maybe a few degrees change on a cam recommendation. Engines build combo dependent to this as well.
Mentioned earlier was the use of cosmetic gaskets. If there OK to use in just a straight swap, great. Call Cometic first to make sure there is no special prep for there gasket before use or you'll have fits like many others do since they often need a special finish before useage.