How much difference will a new converter make

ThanX for all the replies and input. I have a .484 cam btw. I called Dynamic Converters and worked with Shawn and gave him honest info and numbers not "dream" numbers or wishfull ones. I had made some dyno pulls with it last summer just to see what it had and I also gave him all the numbers off my current time slips from the past 3 weeks. I explained I am going to a big block very soon and would be needing another converter for that so I didn't want an 8" extreme crazy converter but I did need his professional advice since it's not my area of expertise at all. His response was the 9.5" 4500-4800 stall. I only asked because I questioned it being higher than I initially planned but this car won't be seing any street time until the big block is back in anyway. I asked about slip and everything else under the sun because it's not a cheap converter. He assured me from my gears, tire size, HP/TQ curve, current ET and current 60ft times and all kinds of other questions that this would be the best combo for this setup. He was also well aware that if it isn't rigt and something goes south, that I would be less likely to recommend or come back to him for my BB converter where I really intend to rake out some serious $$$. I wanted as much input as I could get on this because of the expense and it will be my first custom converter and I wasn't sure what to expect. A few peeps at the track insist it will be like day and night and I just can't see it being such a big difference that's why I went after the big cubes. I will keep you informed of what happens and the results. I can even post before and after time slips for anyone else wondering (keep in mind my rear suspension still needs tuned in). I know I'm losing some # bc of the rear suspension not being top notch. I will install it this Saturday but won't be able to make it to the track until the following Friday night unless Maple Grove has test & tune open this Saturday night. Hope it pays off!!! Thanks for the input.