It is possible to fit 48IDA Webers and use a jackshaft just not the original jackshaft.
We have this installation on our car. Used thick wall chrome moly tubing and with 2 x bearings (no centre bearing) with stout alloy brackets. Still testing Webers vs Holley (we need to change the cam to suit Webers as getting too much reversion / stand off as we call it in UK).
Initially we worried about whip of shaft with just 2 x bearings but critical speed calculations should mean it's safe in operating range we are using, if not we can adjust pulley ratios to slow jackshaft speed vs engine speed. Alternatively its not that big a deal to incorporate a centre bearing coming off one of head / inlet studs.
Installation allows both alternator and a/c (a Standen) pump to run in original location (not shown in the long shot pic yet as A/C not installed for racing).
Torque with this set up is immense!!
