It all depends on your budget and how far you want to go with it..
If you're shooting for more than 500 WHP, it'd be a good idea to start off with an aftermarket block..
I used to run a DSS 331 bottom end, ran it for 3 years with zero problems.. my goal was SC but lost my job and went back to school.. Sold the car to move to CA
Anyhow - Are you looking for a flat out drag car? A fun street car?
What sort of shape is the notchback in?
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2003 Regal GS - the beater/daily driver - somewhat stock (yeah right). No its not a mustang, at least it's blown.
2001 GT Black on Black 5 speed
MM Strut Tower Brace/Weld-In Subframe Connectors/Koni Springs&Adjustables/Cobra Brakes/Cobra Rack/Tri-Ax/3.73s/SCT Tuner 56k miles