narrowing rods

hello AMC'ers:  I'am questioning about how to narrow a rod big eng. I guess its a question for a engine macninist out there. What i want to do is run jeep 4.0l rods in a destroked 360. im using a 343 crank. My plans a to build a long rod engine, like the old 340 mopar (those engines ran great) using the 4.0l rods gives me the length i want but need to be narrowed on the big end to fit the 343 crank.  I know there is also the rod center line to deal with when doing this. So what is the correct way to do this? Hope your answers dont push me away from doing this project. Thanks for reading and giving me your opinons.

I would assume a surface grinder would be the best/easiest way.  But why bother doing this?  I understand the theoretical benefits of a long rod engine, people seem obsessed with "long rods" , and wanting to build something "custom", but the back to back dyno tests I have seen on this show the power gains to be marginal- like 10 HP on a 600 HP SBC when undergoing a sizeable change in lengths.  For the trouble and expense this doesn't seem worth it to me unless you have plenty of $ to spend and are going for every last HP.  IMO it even makes less sense using stock rods.

Only advantage is more torque, but is is enough for how much money you are going to spend?????   I would research it more.............much more..

If you want to do it, then do it.  Most of us have never "really" built an engine trying stuff like that, but have opinions based on what somebody else says that may or may not be true.  It seems that the more recognizable the name, the more "written in stone" that opinion is.  Rarely have I seen real world info to back up claims.  Most are just projections off one engine experience.  Not to knock Stahl, because his is a legendary name, but when was the last time one of his engines won a race?  There are way too many variables and you can build an engine to be efficient for any number of factors.  If there were nothing to the long rod phenomenon, then the high-buck NASCAR guys would not be using 6.2" and 6.3" rods in their engines.  Granted they are carburetor limited and run at high rpm, but that alone should give you some clue as to the characteristics of the long rods. 

Here's another - is it worth less than 2% in this fellow's studies?
http://www.rustpuppy.org/rodstudy.htm
Study his report and the final comments at the end.

Everything on gains and losses is as class guy said, anecdotal at best since you must have a baseline engine study first, then change ONLY what's required to change the rods, then dyno the engine again. In that respect, I must agree with c g.

Go for it, but know - you may see no or little gain - but you may indeed gain. Other factors come into play. Say that your engine otherwise - head flow, carb, cam, etc. are better for running longer rods - you'd gain.
Changing the rod length without considering other factors could backfire - OR you could come out way ahead if your other parts just aren't ideal for a shorter rod engine.
Of course, unless you do this build, then go back to "shorter rods" and don't change cam or head or any other pieces (other than pistons) how can you say you gained or lost since there's no baseline to compare to?

How many people REALLY study the whole, instead of buying parts because so and so said this was a good cam. Good for him and his build, his heads, his flow characteristics, timing curve, etc. Good for you and your parts? Maybe - maybe not.

If every member of the orchestra isn't watching the same baton, it will sound like crap no matter how good the individual players.

Do it and let us know! Maybe even do a write-up yourself...........