you could swap it into any 84-91 CRX but you would be better off sticking with the 88-91 models - the Si model would be the easiest to swap it into due to it already being wired for MPFI - the HF model is also MPFI and is a lot lighter than the Si, but you would need to swap out the front knuckles/hubs in order to use the Integra axles - the DX model would require doing the DPFI to MPFI wiring changes - it is also lighter than the Si model, but not as light as the HF - 88s are the lightest and 91s the heaviest