Beware that 97 octane in UK is the same as 93 in the US.
Blower cams typically have wide lobe separation angles like 114 degrees.
Cast pistons can be used for low boost, say under 10 psi. However, timing and fuel ratio tuning will be less tolerate to mistakes.
On a 350 street build, I would use 7.5-8.0, 10 psi of boost, a cam around 210/220 on 114 LSA, with a good set of aftermarket heads. Expect around 550hp/550ftlbs with this build.
Good exhaust will be important. Headers and dual 3 inch pipes.
Best to just lock the ignition timing. Try 24 - 28 degrees.