300-350 is about what the limits of the VE. You *may* be able to get 400 with extensive modificaitons. You'll be good for 300-350 with the PODs and the HX40. If the HX is toast then you can go to another turbo like the S300 or something but until the HX craps out I'd stick with it. With the right tuning the VE can make the PODs flow enough fuel to get the power you want. If you don't have gauges yet that should be first priority then the 3200 RPM spring. After that you should look into a 4" exhaust if you don't already have that. You may also want to consider a piston lift pump swap to keep the VE fed with enough fuel. An ATS exhaust manifold may help you pick up a few ponies and lower EGTs a little, as will a cam, porting and polishing the head, gasket matching everything, etc. Oh, almost forgot, if you're running more than about 30 psi of boost the head will need to be fire ringed to keep from popping the head gasket which will make you day not so fun.
Your biggest limiter is the A518 which is basically a 46RH. They just can't handle serious power. If you swapping to a bolt action go with the NV4500 with an appropriate clutch for you application.