Can anyone tell me please, where did TRD get the pushrod V-8?

Chevy Ford and Dodge had at least some variant of the engines they run now, I know they move the lifter angle around to suit them. But all had their basis in a mass produced V-8. Where is Toyotas?
Update: as a follow up I know G.M. Ford and Dodge have perfectly good cammer motors why not just run them? or their old long block big head aluninum race motors cut down to 366 cid? They gave Toyota a longer block which=bigger heads
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