High Compression, 10.8:1 for the ultimate in street performance No fuel system or ignition systems included Special head machining fits stock length intake manifolds (S&S manifold size 410) Stock style breathing system; compatible with stock and most performance air cleaners Includes Super Stock heads, crankcases, high flow oil pump, cam cover and easy start cams Specs: displacement 124″; bore 4-1/8″; stroke 4-5/8″; 640 cam; piston type forged flat top Oil line installation kit required. Cylinder heads on T-Series long block engines are 99-05 style. Owners of 06 models will need to purchase a set of 99-05 style, offset intake flanges. Cylinder heads on these engines are specially machined to compensate for the non-stock cylinder length. As a result, they are compatible with manifolds and throttle bodies with stock length intake runners. In addition, the breather vent bolt locations have been adjusted so they are in the stock location, so stock style air cleaner back plates will bolt up to these engines.