tmoss said:I haven't done this (yet), so what is required? Do you have to relieve the cylinders at the bottom for the rods?
Tom, yes you have to relieve the bottom of the cylinders for the rod bolts(ARP 8740 cap screws) to clear properly. I was always told .060"-.080", I like to go .100".
I am torn on this topic, I think the 347 is better in the long run, but with what you have right now the budget 306 will go faster since you have better heads and supporting parts. I would look at a stock replacment aftermarket rid, you can get a cast SCAT for around under $200 and it already has the ARP fastners and is better then a stock rod, espeically one with a lot of miles. You'll need to rebalance it but if your shooting for 10:1 your goig to need different pistons anyway, then you can get a full floating pin design.
Like 25th stated if you race in a local class or track series you may want to really look into it so you don't build something that will put you in a class you can not compete in.
Once you throw some TFS hi ports, vic jr's, afr 185's with a TFS R intake and a custom cam and your making like 425rwhp with the potential to run high 10's on motor you'll laugh at your self for even considering a 306. The 347 is your foundation and you can improve it down the road as money allows. I agree 100% that to go all out on a 347 now is very very expensive. Thats why I bought the Vortech SQ but even that wasn't 'cheap'. I'm hoping the 450-475rwhp will make me forget about the $2300 I just spent