yes, the 88 has different rear suspension - not a big deal as far as i am concerned (i have 88 HF), but if it worried you, just get the 89 HF - it only weighs 15lbs more than the 88 - you would be right that the HF with the Y5 would run like the HX with an engine with 160hp - still, 115hp in a CRX isn't a lot, but a lot more than a stock HF engine - we do a lot of DOHC ZC swaps in the 88-91 CRX/Civic cars and the 88-89 HF with the DOHC ZC and a DX transmission gets around 38-40mpg - the Y5 should be in the same ballpark