My advice is to measure the bike that fits you best/is fastest/most comfortable- 1) Center of BB to top of saddle, along the seat tube; 2) Center of seatpost under the saddle to center of handlebar at stem; and 3) Center of handlebar to grouund while bike is vertical. Even allowing for differences in BB height (which are typically pretty minor), if you set up each bike with these measurements close to one another, they will all fit, be fast, and be comfortable in pretty much the same fashion. As you know, I have a couple dozen bikes and this is what I do to get them all in the ballpark.

Then, individually, I make minor adjustments to saddle fore-aft and tilt; to handlebar angle; and to number of spacers between crank and pedal spindle. I also liek to make sure that when I'm riding each bike in a comfortable position. when I look down the handlebar should exactly obscure the front axle, and when I'm standing to pedal when I look down the front axle is directly below my eyes. Sometimes this means I have to change a stem by 5 or 10 mm, but it makes a difference.

Finally, I'm a big believer in quality wheels and quality tires. Big fan of quality hubs laced to mostly modern Open Pro level rims with double butted spokes. Everything I ride is clincher, and I limit tire selection to Vittoria Open Pro III (no longer made but still out there as NOS), Continental Grand Prix 4000 SII (ditto, and even slightly less expensive), Vittoria Corsa G (especially when looking for the skinwall effect), or Panaracer Gravel King file tread (brownwalls that don't go with all paint schemes). None of those tires are cheap, with prices ranging from $32 to $59 per tire, but th data I've collected over the years tells me that they last a long time, give a good ride, and don't hold me back on speed.

Anyway, just a few data points that may help you enjoy your Ironman. I certainly like my '86 IM, and consider it to be as sublime a ride as just about anything else in the stable.