Hooker Competition Headers

You can not instal the engine with the headers on into the car and removing the T bars would help with clearance but it would probably be more of a PIA to do so. The T bars do not go through the header.

Before getting the engine in, install the header(s) and hold it away from the engine with bungi cords. Leave the header rapped in the shipping plastic to retain best cosmetic looks after your done.
IMO, the studs at the ends are very helpful to install the header. You can hang the header (& sometimes the gasket as well) on the studs so you can start with the bolts on the tight bend tubes first.