it can be realistic but not going too crazy like puting a Viper engine in a Honda Civic... it has to be with the most common engine swaps only... like LS1 engines in RX7, Miatas, BMW M3 and other 3 series... or an H22 or K series in a Civic, maybe the Accord V6 engine in a Civic, Mustang engines or LS1 engines in Volvos.. have the 4 cyl Duratec Cosworth engine abailable for many rally & race vehicles... etc... it can be done & they will have to measure new PP points for a vehicle after an engine swap & performance upgrades... hope to see this one day in GT6 or GT7 for PS4 if it ever comes out in the near future...lol