Poly Engine what was good/bad about it and why is the LA better?

MOPAROFFICIAL said
LA- Light Assembly.

The polys weight and its width killed the versatility and the heads lacked high power potential. They didn't peak as high as the later LA's do, they were wider, they weighed more and cost more to to produce. There were a couple cool versions and if you get one of the earlier Poly ' the 325 or 315 or somesheet'...maybe it was the Windsor poly/hemi ..anyhow someodd cid..you could swap that early particular truck hemi head onto the odd ball early poly.
It may be the truck, 315 or whatever poly that is the one that accepts the pre passenger car 'not the 392/354/331/241 stuff ' but the truck indust type hemi heads.

270, 315 and 325 Dodge poly motors, plus 301, 331 and 354 Chrysler poly motors can all be converted to hemis, using Dodge hemi heads on the Dodge motors, and Chrysler hemi heads on the Chrysler motors.

57 DeSoto Firesweeps were basically Dodges with DeSoto trim, and used 325 Dodge poly motors. These can be converted to hemis with Dodge hemi heads. There was never an actual DeSoto poly.

Plymouth used Dodge poly motors in 55 and in lower line 56 models without power pack, in 241, 260 and 270 inch versions. These can be converted to hemis with Dodge hemi heads. The actual Plymouth poly (277, 301, 303, 313, 318 and 326) is its own motor, not based on any hemi motor, and cannot be converted to hemi.