I assume you mean a 93 Allante. No such thing as a 95 Allante.
Forget it. Anything later than a 1999 would be virtually impossible to get running in a 93 Allante. The Northstar engine changed significantly starting in 2000. In addition to the mechanical changes (roller cams, new cylinder heads, intake manfold, coil at plug ignition, etc...) the electronics of the engine and control system went to a completely different generation of controller and ignition. Impossible to adapt the old to the new...or vice versa. Even the crank sensors, crank sensor location and crank shaft reluctor wheel pattern changed....and are totally incompatible. The 2000 and later control system will not even run as a standalong system outside the cars it was developed for and if the car WAS rewired for the 2000 and later system the dash and such could not talk to the PCM. Forget it.
The only practical engine for a 93 Allante is a 93/94 vintage engine. Even a 95 or later requires significant rewiring, replumbing and cobbling of the engine support hardware. I would recommend sticking with the original engine.
What is the goal of the "upgrade" you envision? A 93 engine can be easily "refreshed" to like-new condition. There is no more power or driveability in a later engine so there is very little to gain by substituting a later model engine in the car.
Thanx for the replies. Yes - '93 - fumblefingers in original message. Looking to replace engine because one in the car locked up. 100k mi engine religiously maintained but .......... 9500 mi 2001 engine readily available from wreck. Guess I'll forget that idea. Thanx again.
Couldn't you use the block and heads (or at least the block) from the 2001 and use everything else from the 93??
No, not at all. The heads are completely different on the 2000 and later engines. The block itself might work but for a few details: The crank in the 2000 and later engines is completely incompatible with the 93 electronics because the reluctor wheel pattern is different. So the crank from the 93 would have to be used. The block won't work because the crank sensor locations are slightly different so the 93 crank sensors wouldn't work in a 2000 and later block even if the 93 crank were installed.