73 front clip?

Nope.

They would physically bolt on, but you'd also need the '73 beak, hood latch panel, grill, bumper, etc. Basically everything that unbolts from the doors forward would need to be switched, and then you'd have a '70 that looks like a '73. Most folks would say you're doing that backward, as the '70 front end is a lot more desirable than the '73.