Are there any links/info on which is the best fwd skoda engine to use for rear engine skodas (s types)

i pretty sure its a topic already done somewhere, my 120 seems to be running fine and fast on unleaded without any retuning or anything since it was introduced but i will be returning my s types back to the road soon, i do have a 135 ric engine with the unleaded headas i have three s types atm i probably gonna be on the look out for a few unleaded donors, either that or have someone engineer some hardened valave seats/valves?

 

any info would be appreciated

Don't worry about unleaded for the 5 port engines unless you're planning on thrashing them......never yet come across anyone suffering valve seat recession. It usually only significantly occurs on high mileage high rev engines. I doubt you'll do either in an iron head Skoda.