The rear engine mount sits about 4 inches behind the crossmember and unfortunately cannot be easily supported on this.
Unlike other 4 speed conversions dealt with next.
Opel, M-20 / M-21, Saginaw / Muncie / T-10, Borg Warner, Borg Warner Single Rail / Top Loader / Datsun / Toyota / Mazda,
OPEL: By far the easiest and neatest 4 speed conversion for the early holden. It fits in with little effort only minor
denting of the floor crossmember for a RH linkage. The Opel clutch must be used with an 8-3/8 inch pressure plate and all
fits up well. Either gearshift can be used. Torana type (on extension housing) or Monaro (remote floor mounted) and the engine
mount at rear aligns with the floor crossmember. The standard speedo cable fits, and the FB/EK manual tailshaft, with Opel
yoke fitted is the correct length. The mechanical clutch connects up well and no other floor clearance is encountered except
for the breather - as per Datsun. Rear crossmember can be owner fabricated and is equally ideal for sedans as it aligns with
some area of strength to mount if from. This box can be mounted to either grey or reds with engine mount adaptors for grey
being available as per M-21 gearbox.
Opels contrary to popular rumour aren't that bad, for when in good condition give little trouble, and only really broke
when fitted to heavy vehicles with tall diff ratios and in an early holden are a very rewarding conversion
The best Opel to use is a Torana type with shifter on extension housing and fitted with the cast iron base plate as this
is the revised gearbox and is the stronger one available. Heavy duty clutches are available and extremly rare, as no one considers
it necessary to stock such an item.
AUSTRALIAN 4 SPEED (M-20/M-21)
Same basic gearbox as the all syncro, except with another gear inside and reverse placed in the extension housing. It shares
a common clutch, bell housing and overall length and spline on output shaft, but it involves quite major floor and crossmember
surgery to mount the gearbox successfully. Any floor or crossmembers that have to be cut must be rebuilt to maintain adequate
strength for a roadworthy conversion.