We ran Fontana’s and have just recently switched to a sr11. Loved our Fontana’s have low end torque and don’t need to twist them. Have a spec 7 for sale with everything to put in a car if interested. Was Andrew Felkers motor that won many powri races. Never been a fan of the esslingers. Really only getting rid of our Fontana because everything is different than our sr11 so don’t like keeping spares for both. Good luck in whatever you decide on getting.