any toyota motor that has a G series head means it was designed by yamaha. which means it was a performance head with a different bottom end to support the performance of the head. an F series head has a narrow valve angle and was designed for everyday use and gas mileage. and the bottom ends were weaker. yamaha has been helping to design and build toyota heads since the 60's when the 2000GT came out. which shares the same engine family lines as the 4me, 5me, 5mge, 7mg/gte. so you can say that the chevy small block has been around but its also true of toyota motors as well.