Sorry to hear mate. I went through the same thing after owning my car for 2 weeks with 55k km on the clock - bent 2 rods and ruined the block. I initially went down the F6 short motor path because at the time, it suited my budget and my desired power levels. But 1.5 years later, I started wanting more and went down the built motor path. Initially, I was getting a shop to do the work and my budget was around 20k for under bonnet work only. A few months later, I wanted to go a little further with it and my budget became 50k including the drive train. I think you need to look at 2 or 3 main things. Are you planning on doing much 1/4 mile stuff, how much power do you think you want to make and what is your budget? Answering these things will dictate what to do I reckon. I think for the high 300's rwkw, an F6 short (add valve springs and billet oil pump gears) with a 'safe' tune and well maintained, can last you years. Of course, doing regular 1/4 mile work with an F6 short on higher power levels will change that. Going the F6 short could cost you as little as the 6k mark depending on who and what you know. Building a forged bottom end will add a few k to that depending on what you do.