I know this thread is a bit dated, but for future reference:
351c engines use the same engine mounts, bellhousing, flywheel/flexplate, and balancer/pulleys as a 302/351w.
Swapping in a 351c will be much the same as swapping in a 351w.
The biggest things you need are a Fox oil pan for a 351c and headers.
If you didn't get the distributor you needed for your ignition, then that is needed as well.
If you are going to keep your EFI/TFI, you can do so with a 460 TFI distributor and a Trickflow 351c EFI upper/lower.
The 351c uses the same firing order as an HO 5.0, and the 460 distributor interchanges with a 351c, so with the TF EFI intake, you can use your fuel rails, injectors, TB, etc, and go full on EFI 351c.