1977 440 out of a van.

In addition to the Schumacher mounts (that I would recommend as well), he sells "Magnum" mounts which are designed not to fail and rip apart as the old rubber biscuit mounts from the factory would eventually do. The van would have used the later spool mounts which were a better design. So your basic choices are: modify your k-frame for the spool mounts or just buy the Schumacher mounts for your K. The latter will be just fine. Either motor mount will bolt to your block.

A torque strap is totally optional. There shouldn't be a bunch of vibration unless something is wrong. No need to change the trans mount or cross member.

The 452 heads will flow pretty similar to the 906 and they already have the hardened exhaust valve seats.

The later big blocks like that have the water pump inlet on the passenger side. Just something to consider when sourcing a radiator. Cast crank, externally balanced with a thick damper.

Be prepared to upgrade the brakes (discs in front), suspension, and a larger rear diifferential if you have the small one.