S type manual gearbox swap

[magpies]

Hi
I'm looking at fitting a 3.0 V6 engine to my TVR S (In place of a tired Cossy v6) I will be using a stand a lone management system (Emerald K6)

so won't be using the Jag brain along with all the associated parts.

Question is - most 'cheapish' S Type cars are automatic, Manual gearboxes are available at a reasonable cost.

What are the pro's / cons for the 5 and 6 speed boxes presuming both will fit