Assuming that you have an automatic transmission, this is a pretty involved process,so ask your self if it's worth the effort and expense.You need all the parts for a manual transmission swap. These would include, a manual transmission,a bell housing,a clutch and pressure plate,throwout bearing,another type flywheel,all related linkages,all related linkage and pedals for inside the car,another type of shifter,and possible driveshaft and crossmember change. It is possible,but not an easy option. .
See the garage-scene web site link to the right.
If it is an automatic 3 speed, it is probably a TH350 tranny. an overdrive tranny which is just about the same length and requires almost no modification is the TH200-4R. most of these trannys are a Buick, Olds, Pontiac bellhousing design but there are some that have a Chevy bellhousing too.
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The 1984 elc had the option of the 200r4 4 speed, everything older does not. The 200r4 is great because of the multi-use housing. Because the subframe is shorter on everything older then a 1984, you have to get either the transmission mount, on the original cross member, cut and rewelded 6 inches + a little (or on the back side of it) to the rear. Or you can order a new (fabricated) Crossmember with a subframe extender @ $300. I don't know if this holds true for a V-6.
Pretty easy because there was no El Camino SS in 1978.
Yes
Doors from a 1978-87 El Camino or GMC Caballero
Any 1978-87 El Camino or GMC Caballero
187 inches
There was no El Camino SS in 1981
From 1978-1987
The back glass from any 1978 or newer El Camino or Caballero will work.
Yes
Yes
The model is a 1978
probably a th350.