Anybody ever try to build one of these? Me and a couple guys from work are interested in designing and building one, don't wanna spend $10k on a Central Boiler. Suggestions?

It's harder than it sounds to achieve reliability and good performance... I haven't personally built one but a relative of mine has built several... he has some growing pains... and I've seen some other home-built units... most notably one that can completely obscure a 4-lane interstate highway I frequently drive on because it belches so much smoke out... I can't imagine trying to feed that thing when it's wasting so much energy out the chimney like that... and when the wind blows in the direction of the house I wouldn't want to be living there...

If you do your research and "copy" commercial designs you shouldn't have any problems. If you cobble something together with no idea what you're doing you will have plenty of problems... I advise you look at a lot of them in-person inside and out, ask if you can take access panels off etc to see all the workings. Note the brand/size of circulation pumps, blower motors etc...

How much DO you want to spend, and what output do you want?
Indoor and outdoor models are available a lot cheaper than CB.

Head over to The Arfcom of Woodburning and do some reading.  Lots of pictures on most every gasification boiler made, and some homemade ones too.

I know a guy who had great success building a Garn type boiler, 5 pass, out of a 2000 gallon oil tank.  He hasn't filled his propane tank in four years.

Thanks for the info, that's what I was looking for. I haven't done the calculations as far as BTU's but I would need to heat 2800 sq ft through radiant floors. I've come up with a design and priced the steel for a 3' x 3' firebox and associated water jacket steel, came out to ~ $3200 for materials. 3' might be a bit excessive and I will likely shrink that down. Anyways, a buddy of mine is wanting to build his first in the spring so we'll see how it goes, I'm sure I'll learn a few things. Thanks for website reference.

I don't have the tools or welding skills to build one, but if I did, I would build something like the Garn boiler, and put it in a good shed.  Project costs go way up, but the Garn is impressive.  Is your system existing, and if so, what water temperatures are you running?