Ahh
I don,t know anything about using a Toyota twin cam motor ...
Basically the position of the engine is usually dictated by the gearbox used, to ensure the gearbox bell housing fits then work forward with the engine then position the engine mounts where they are needed....
A good idea is to plate an area flush with BR1 & BR8...BR2 & BR9 mid way along the triangle that these rails create, then once you know the position of your engine just fabricate some mounts from the block down to these welded in plates.
Just a note..... keep in mind the position of the steering column as depending on the mounts you fabricate it might be in the way
sorry if this isn,t very helpful to your request for info but I have no knowledge of the Toyota motor.
cheers
andy