The dual inlet will work fine. The 5 holer parallel is easier to tune abiet harder to drive.. sequential is possible but needs more time to tune as you may need to add a secondary fuel table.

One TPS is fine - put it on the primary.

Remind me if the GMC is a 12 port head...

51 GMC 4.2 turbo
Can't solved today's problems using the same technology/thinking that created them