To continue the build or not...?
Alex, just build the buggy. There's too many variables from one buggy to another to consider putting anything off until you get measurements. 2 buggies who have the same engine configuration, the same chassis, and the same body, may have much different clearance measurements. You have to consider the differences in pan shortening, and the way the body was mounted to the chassis. Deal with the issues as they come, or you'll go insane. If you can't afford a part you need to continue the build, spend more time with what you DO have. Use that time to straighten out the wiring harness, clean your transaxle, paint your axle tubes, whatever. I'm sure you can fit your Type-1 engine in with dual carbs, one way or another, without having to hack the body. You MAY have to move it up on the chassis a hair, or shim it in the back, buy shorty manifolds, etc.
I have seen the carbs have clearance issues. Alot of it depends on the style of the rear of your buggy. My center mount carb only has 1/8" clearance from the body and at times it touches. The bigger problem I see with carbs is the exhaust clearance issue. As for oil coolers you have options. I looked into other coolers but the stock one works very well on my 1900 street use buggy. I would suggest the additional oil sump it is my understanding this helps cooling a great deal. http://www.dansperformanceparts.com/buggy/osc/buggyosc1.htm
I am CHEAP.......I found a type 4 in a bus that comes with the bus minus the transaxel for $200. It is fuel injected and may remain that way if I can't find some cheap webers on ebay. The motor is a fairly quick thing to upgrade down the road when you have a few grand to toss at it. They drive fine with a crappy motor, just bring a few qts of oil and a cell phone with you. And tell everone it is a diesel if it smokes too much.
thanks guys, I was just looking for opinions on this as I didnt want to tell you after I had the whole buggy done that I had to tear it down and start all over on the build because of and engine clearance issue Even you guys would be crying for me, after spending months and $$$$ on something that doesnt work... thanks again! watch out you're the ones Ill be consulting when the engine doenst go in jajaja!