Why ruin a good plane?
I thought the OP was asking about buying a 6 and converting to a 6A. (His sig says WTB 6A)
I've seen the question before. I've never seen it quantified, but buying a flying RV and moving the third wheel has never been suggested as 'doable'.
Switching during build has been described, and has its cost drawbacks.
I think in this case the advice should be "Buy the plane you want to buy"
While I agree with Rockwood's comment, my question is why do you want to make the change?
I agree 100% with Scott. On the -6 this is not a project to be taken on by a non-builder.
Performing the operation like Gil suggests would be marginal. It would depend on how accurately the original builder reamed the steel splice plate attach. Without the additional carry through section, there could be a little slop.
This is, of course, my opinion and worth exactly what you paid for it!
I don't think that would be a problem Mel because the original drilling done by Phlogiston was with the spars, both splice plates and the bulkhead all fixtured and drilled in assembly. The biggest issue would be properly positioning the weldments laterally so they matched up flush to the lower longerons. Not something that I would look fwd to doing.
Just plan on a small error in the inwards direction and make a shim to fit.
I think careful measurement from the outer bolt hole to the longeron would get you very close so the shim needed would be of minimal thickness.
Lots of trimming/ grinding to make the bolt heads/nuts fit the differing thicknesses of the gear mounts will be needed anyway.
The forward mount to the longeron never fit very well anyway and can be bent to conform, and shimmed if needed - which mine needed.
Yup, I know... I have been through the whole process numerous times.
Primary point for this thread... it would not be an easy process regardless of how you did it.
Converting a 6A to a 6 would be no big deal.
Aloha,
How difficult/$ to convert a TW (6) to a 6A?