Are these engines the same basic unit(DOHC of course) from 91-95? Is it possible to bolt the 1.8L in the MX3 as a complete swap?

yes it is but goin from the mx3dohc b6 to the 1.8l bp out of a escort gt is a bit of a painn as the b6 is maf and the bp is vaf-wirin is a pain. if u have the dohc 1.6 go turbo as its the miata motor and is good under boost, but if u have the sohc mx3 the escort gt 1.8 4cyl bolts right in same tranny wirin harness just have to run 2 wires for the vics bp vaf and ecu can be used on te stock wiring harness too. the dohc b6 in the mx3 94+ will interchange with ne miata part with the b6 dohc, cams , internals, udp, etc. the 1.8l bp from the escort gt is the same as the 1.8 in the miata also but once again with less aggressive cams etc. 1.8l miata parts interchange. both the dohc b6(mx3) dohc 1.8bp(escort gt, protege some kias,etc.) came in the 323 gtx which is a turbo version of both motors so u can get the turbo manifold for either one for cheap as well as turbo related parts.