Moving the engine back

If it's a back-half car I'd think it would help a bit because of how the weight transfer is handled and how it affects the rear suspension. A purposebuilt tube frame car it's less of a bonus. That being siad I think the distance needs to be greater than 3" for it to really help much. It's a ton of work in a production car nose. Headers and engine servicing (like valve cover removal and head removal) are the hardest things to overcome.